~ Baby Roach ~
When Geralt arrived at the lake, he easily found the kelpie he was sent here to hunt. It was slumped over, half-in half-out of the water, already dead. At first he didn't notice the tiny form huddled against the corpse's bulk, but as the witcher turned to leave, the kelpie colt struggled to its spindly little legs and toddled after Geralt.
"Stop following me," Geralt said.
The kelpie colt either could not understand what he was saying, or did not listen.
By the time he made it back to where his horse was waiting, he'd named his little horsey shadow "Baby Roach".
A few months after he'd first taken her in, Baby Roach figured out how to turn herself into a human-looking toddler, which she did when they were passing through towns.
She even began to speak while in human form, although she didn't say much other than "Papa" at first.
Which caused some problems for Geralt, since he didn't know what he should call her when she was in her human form, because calling her Baby Roach did not sound right and hadn't gone over well in the one town where he'd done it.
Eventually, he took to explaining her presence as "This is my daughter." And if people happened to ask what her name was (Geralt was surprised at how often they didn't bother), he would awkwardly reply, "Um... Dottie."
Most of the time, people wouldn't question this. However, sometimes someone would reply, "Short for Dorothy?"
To which Geralt would reply with a hmm which his interlocutor would not know how to interpret. It was not short for Dorothy, it was short for daughter, since Geralt had still not come up with a good alternative and panicked when he was put on the spot. Somehow he never managed to remember the name Dorothy until it was too late the next time one of these rare conversations occurred.
It wasn't until after they'd met Jaskier that Geralt finally picked out a human-sounding name for her, and started calling her Daisy. Daisy would have worked just as well for a horse name too, but Geralt still called her Baby Roach whenever she was a horse.
Jaskier had never really questioned the fact that Geralt had suddenly adopted a child. He assumed the toddler had been orphaned by a monster that Geralt had slain, or something like that. Geralt might like to pretend to have no feelings, but he was really a big old softie at heart.
He had protested the uncreative name Geralt had called the child, and was pleasantly surprised when his suggestion of changing her name to Daisy was taken seriously. He thought he'd once heard him calling her Baby Roach, but surely that was just the bard's ears playing tricks on him. Not even Geralt would a name a child after his horse...
Jaskier discovered the truth behind that assumption soon enough, when he offered to bathe the child one evening to give Geralt a break.
Once he placed the toddler into the water, he got the shock of his life. The sight of the creature that was now swimming in the bath water prompted the bard to let out a panicked shout.
By the time the witcher entered the bathroom, the creature had leapt out of the water in the form of sleek black colt, shaken herself off and sprayed water all over the room (and Jaskier), and then turned back into the sweet little toddler that Jaskier knew and loved.
"You said you could handle bathing the child alone," Geralt said.
"You could have warned me that she's a kelpie!"
"... I thought you knew."
Baby Roach raised her chubby little arms and called out plaintively to the bard, "Askee!" (Which was as close as she'd ever gotten to pronouncing his name.)
Having recovered most of his composure by this point, Jaskier leaned down and scooped the child up.
She snuggled into his shoulder.
After a few minutes of cuddling, the child inquired, "Baff?"
"Yep, time to finish your bath," Jaskier replied. "You like baths, don't you? Who's a good little water creature?"
"What a pretty little horse! She looks like a kelpie! What's her name? Is it Kelpie? I'm gonna call you Kelpie!"
Once Geralt managed to get a word in, he said, "Her name is Baby Roach."
Ciri reached out to pat Baby Roach, who snapped at Ciri's fingers before hiding behind big Roach.
"... and she is actually a kelpie," Geralt added belatedly.
Several hours after they'd made camp for the night, Geralt was awakened by the sound of Ciri shrieking. She sounded more indignant than truly distressed, but Geralt rushed to her aid with the same amount of speed as he would have if she'd actually been in danger.
What he found was two little girls so covered in mud that he couldn't tell who was who until one of them called out, "Papa!"
"Daisy, what happened?" Geralt asked, instinctively using the 'human' name which he called his daughter by in this form.
"Daisy?" Ciri repeated, nonplussed.
Baby Roach pointed an accusing finger (still dripping mud) at Ciri, and said, "She sat on me!"
From this, Geralt could extrapolate that Baby Roach had chosen to sleep in her horse form, and Ciri had sat upon her back in an attempt to ride her. True to the instincts of her species, the young kelpie had carried the human girl to the nearest body of water and attempted to drown her. The nearest body of water had been a shallow puddle, which resulted in no one drowning but both children becoming covered in mud.
"Ciri, do not sit on your sister. Daisy, do not try to drown your sister."
To which both girls promptly replied, "She's not my sister!"
Which led to Geralt having to hold them apart as they both moved to tackle one another back into the mud.
"You're sisters now, and stop trying to fight each other!"
Suddenly he felt more sympathy for Vesemir.