She was one of the oldest fairies, but that didn't mean much. She was also the different one, the one who was more curious, bolder, the one who sometimes wished she could have an adventure or do something once in awhile but collect teeth – not that she wasn't devoted to her job, just like her sisters. It was just...

They were all meant to be the same, even acted more like a hive mind at times. They weren't proper individuals, didn't have names, didn't have a way to call each other besides sister.

But...she did. He'd named her, their Jack Frost, set her apart from her sisters.

He didn't even know what that meant, to be given a name. Choosing one meant you were declaring yourself as a personality, but to be given one...

Later, when he found out they didn't have names, he brought lists, gave them all the chance to choose names for themselves, freely, as a gift. It didn't affect her sisters the way it did her, since it wasn't a spontaneous choosing, but they were all so very happy.

She had stubbornly stuck with her name, proud to be Baby Tooth, that it meant she was the real baby of the family, the favorite, but when he whispered his choice to her...

Just between them, a secret name to bind them closer, although he didn't realize what he had done, to name her twice, and make the second one so carefully chosen, offered so gently. The first could have been brushed off as a spontaneous act, ignored so that things would be the same, but not one this carefully chosen and offered like the precious gift it was.

Rani, he whispered to her, his Rani, his little princess, little lady, the special one.

Accepting it would change everything – and yet she wanted it more than she'd wanted anything before in her very long life.

She'd worried about telling her mother, but she realized Mama already knew when she gave her the tiny coat in her size, presenting it to her with understanding and gentle eyes. Mama always knew.

Jack, of course, had no idea. He worried about her spending so much time with him, that she would get in trouble. She tried to reassure him as best she could that she wasn't disregarding her duties, which grew easier as time went by and he began to understand her more and more – and Mama lessened her duties bit by bit.

Still, it wasn't until he saw her next to one of her sisters a decade after joining the Guardians that he began to understand.

She was taller than her sister, barely a quarter inch, and her feathers were more blue than green now, her beak shorter with a curve coming on the tip, more blue jay than hummingbird.

Jack freaked. When Tooth let him know it was because he had named Baby Tooth, and claimed her, he panicked worse, retreating to the rafters in shame. He'd never meant to change her and take her away from her family!

It was the first the other three had heard of it, since they hadn't paid much attention to the baby teeth before.

They were so busy watching Tooth with the distraught Jack that they didn't notice as Baby Tooth panicked. Jack...didn't he want her? If he did...why was he...with a tiny chirp, Baby Tooth flew out the window in a blind panic.

"I...I never meant to take her from you," Jack said in a tiny voice as Tooth settled next to him. Whatever she was going to say was lost in a sudden surge of new, stronger panic as a new instinct made him look out the window, where his muddled emotions were kicking up a blizzard.

He froze, the rafter around him icing over in a sudden shock freeze. "Baby Tooth! Baby...Rani, wait! Come back!" he cried, diving off the rafter.

He was out the window in an instant, his frantic worries making the storm kick up harder around him. A hand touched his shoulder and he spun to find Tooth behind him, shivering and barely able to keep upright in the fierce wind.

"Jack! Is Baby Tooth..."

"You need to get back inside," he called back, almost having to yell to be heard over the storm. "You'll get hurt out here! I'll find her, don't worry!"

"But..."

"Please, Tooth," Jack pleaded, grabbing her arm in his free hand. "This is my fault, and the cold doesn't bother me. It's too cold for the rest of you!"

Tooth hesitated, but the wind was whipping and tearing unmercifully at her feathers and wings, threatening to take her out of the sky or shred her wings at any moment. Reluctantly she returned to the window as Jack shot into the wind. He wasn't sure why or how, but he had a faint sensation of Baby Tooth and he followed it blindly. He had to find her before it was too late!

Baby Tooth fought her way through the wind, frightened and confused and completely, utterly lost. She had thought she was getting more used to the cold, and she could stand colder temperatures longer than her sisters, but this was more than she was ready to handle.

No wonder Jack didn't want her, she wailed silently, She was a failure as a tooth fairy and now she'd failed at being his companion.

She'd been so happy, thinking she'd finally found her special place, since he'd given her a special name and everything, but the look of terror on his face when he realized how she'd been changing...

She thought she heard Jack calling her names, both of them. Could tooth fairies die from the cold, she wondered, or did it just make them hallucinate?

Either way, it wasn't that bad of a hallucination. With a sigh, she let her wings fold and fell out of the sky, barely conscious of chilled hands catching her as their owner darted back to the Pole with the speed of his storm.

She woke slowly to find herself wrapped in a warm cloth, with a chilly finger stroking over her head slowly, touch so light and gentle she barely felt it.

Slowly her eyes fluttered open and she saw Jack smiling down at her gently, his eyes so full of love she felt her own spill over even as she huddled down into her blanket.

"You gave us a scare, little princess," he said, his voice soft. "Why did you fly out in that storm? Am I teaching you bad habits?"

Baby Tooth chirped quietly and hung her head, refusing to look up at him. She heard him sigh as he held her closer to his chest, curling around her. "I was afraid, Rani," he said, using the private name he'd given her. "I thought I'd taken you from your mother without even giving you a choice, and I didn't even realize what I'd done to you until I saw you next to your sister. I'm so sorry, I never meant to..."

Baby Tooth chirped frantically, cutting off Jack's apologies. He tilted his head, listening carefully as she demanded he stop apologizing, telling him how she could have rejected the changes since they weren't forced on her, all she would have had to do was reject the name, and shamefacedly admitting that she ran since she thought he didn't want her.

She only got so far into her explanation of how he must not want her before cool lips pressed to her head. "You're one of the best things that have ever happened to me, Rani. Don't ever doubt that. I do that enough for both of us." She giggled, bumping her head against his chin. "C'mon," he said, standing and cradling her blanket carefully in the crook of his arm. "Your mama's waiting with the others to find out if you're okay."

Baby Tooth felt warm enough to fly again by the time they reached the small room the other Guardians were waiting for them in but stayed in her blanket, content with being carried by her Jack.

The others perked up as Jack entered, looking visibly relieved as he sat next to Tooth with an obviously healthy Baby Tooth cradled close to his chest.

"...I still don't know if I understand this whole thing or how naming Baby Tooth makes her mine," Jack said quietly, "but I never meant to take her from you."

Tooth patted his hand, smiling at him softly as Baby Tooth chirped and squirmed out of the blanket to settle herself under his hoodie into the hollow of his throat, rubbing her tiny head against his neck. Almost automatically he drew his legs up to his chest, wrapping himself around Baby Tooth.

"I know," she said just as quietly, "And as I was trying to tell you, it's all right, Jack. You and Baby Tooth are a good match, and I'm sure you're going to be happy. There are some who might have tried naming one of my girls to take her from me, but you never would. And you protected them from that."

"The lists of names," she said when he glanced at her from under bangs, still not moving from his protective curl around the tiny fairy in his hoodie. "They've chosen their own names now. No one else can name one and bind them together again, unless my girls choose it. Though I would appreciate those lists, in case I ever have to expand the operation again."

"You've got them," Jack promised. "I'm just glad that didn't mean I took all your fairies by accident. I just...it was an accident. I shouldn't..I don't deserve..."

There was silence for a few minutes, only slightly awkward, until Tooth suddenly fluttered off the couch to hover in front of Jack.

"I have an idea. Baby Tooth, come here for a moment." Baby Tooth cocked her head, looking up at her mother for a brief moment before fluttering into her outstretched hands. "Jack Frost, the one you have named Baby Tooth," she began formally. Baby Tooth fluttered up to whisper to her mother quickly. "Really? When did...when he gave names to the others? And he picked that for you too?" Baby Tooth giggled, making her mother smile as she flitted back down to sit in her hands.

"What was that all about?" Bunny asked, as North watched with eyes glittering in amusement. Sandy was silently laughing, clapping his hands with glee.

"Jack gave Baby Tooth a second name when he let my other girls pick theirs," Tooth said proudly. "She was keeping it to herself. And it's perfect."

She turned back to Jack, who was watching them with silent confusion and hope growing in his eyes. "Jack Frost, the one you have named both Baby Tooth and Rani wishes to stay with you. Will you promise to love her, to care for her and keep her safe, to hold her dear to your heart and assume responsibility for her, as she is now bound to you by your naming of her?"

Jack's grin was blinding in his joy as he realized what Tooth was doing. "I will."

Tooth grin was almost as joyful, though there was a tinge of sadness there as her Baby Tooth left the nest. She held out her hands to Jack, holding the fairy out to him. "Then I put Rani – Baby Tooth – into your hands, Jack Frost." She suited action to words, gently placing Baby Tooth into Jack's cupped hands, biting back a coo as he immediately cuddled her daughter.

He brushed a kiss over Baby Tooth's head and leaned against Tooth when she rejoined them on the couch, Baby Tooth's happy chirps echoing around them as she cuddled into Jack's hoodie happily.

It was an odd feeling, to know one of her fairies was someone else's now. But in that moment, Tooth was sure there was no one else in the world she would trust with her little girl.

A/N: Pulled from the prompt jar "What's in a Name", and this is what it inspired. I hope someone enjoys.