The following is an annotated version of the fairy tale. I recommend reading the entire story before exploring the annotations, especially if you have not read the tale recently.
ONCE, a long time ago, there was a gentleman had two lassies. The oldest was ugly and ill natured, but the youngest was a bonnie lassie and good; but the ugly one was the favorite with her father and mother. So they ill used the youngest in every way, and they sent her into the woods to herd cattle, and all the food she got was a little porridge and whey.
Well, amongst the cattle was a red calf, and one day it said to the lassie, "Gee that porridge and whey to the doggie, and come wi' me."
So the lassie followed the calf through the wood, and they came to a bonnie hoosie, where there was a nice dinner ready for them; and after they had feasted on everything nice they went back to the herding.
Every day the calf took the lassie away, and feasted her on dainties; and every day she grew bonnier. This disappointed the father and mother and the ugly sister. They expected that the rough usage she was getting would take away her beauty; and they watched and watched until they saw the calf take the lassie away to the feast. So they resolved to kill the calf; and not only that, but the lassie was to be compelled to kill him with an axe. Her ugly sister was to hold his head, and the lassie who loved him had to give the blow and kill him.
She could do nothing but greet; but the calf told her not to greet, but to do as he bade her; and his plan was that instead of coming down on his head she was to come down on the lassie's head who was holding him, and then she was to jump on his back and they would run off. Well, the day came for the calf to be killed, and everything was ready -- the ugly lassie holding his head, and the bonnie lassie armed with the axe. So she raised the axe, and came down on the ugly sister's head; and in the confusion that took place she got on the calf's back and they ran away. And they ran and better nor ran till they came to a meadow where grew a great lot of rashes; and, as the lassie had not on many clothes, they pu'ed rashes, and made a coatie for her. And they set off again and traveled, and traveled, till they came to the king's house. They went in, and asked if they wanted a servant. The mistress said she wanted a kitchen lassie, and she would take Rashin-Coatie.
So Rashin-Coatie said she would stop, if they keep it the calf too. They were willing to do that. So the lassie and the calf stoppit in the king's house, and everybody was well pleased with her; and when Yule came, they said she was to stop at home and make the dinner, while all the rest went to the kirk. After they were away the calf asked if she would like to go. She said she would, but she had no clothes, and she could not leave the dinner. The calf said he would give her clothes, and make the dinner too. He went out, and came back with a grand dress, all silk and satin, and such a nice pair of slippers. The lassie put on the dress, and before she left she said:
"Ilka peat gar anither burn,
An' ilka spit gar anither turn,
An' ilka pot gar anither play,
Till I come frae the kirk on gude Yule day."
So she went to the kirk, and nobody kent it was Rashin-Coatie. They wondered who the bonnie lady could be; and, as soon as the young prince saw her, he fell in love with her, and resolved he would find out who she was, before she got home; but Rashin-Coatie left before the rest, so that she might get home in time to take off her dress, and look after the dinner.
When the prince saw her leaving, he made for the door to stop her; but she jumped past him, and in the hurry lost one of her shoes. The prince kept the shoe, and Rashin-Coatie got home all right, and the folk said the dinner was very nice.
Now the prince was resolved to find out who the bonnie lady was, and he sent a servant through all the land with the shoe. Every lady was to try it on, and the prince promised to marry the one it would fit. That servant went to a great many houses, but could not find a lady that the shoe would go on, it was so little and neat. At last he came to a henwife's house, and her daughter had little feet. At first the shoe would not go on, but she paret her feet, and clippit her toes, until the shoes went on. Now the prince was very angry. He knew it was not the lady that he wanted; but, because he had promised to marry whoever the shoe fitted, he had to keep his promise.
The marriage day came, and, as they were all riding to the kirk, a little bird flew through the air, and it sang:
"Clippit feet an' paret taes is on the saidle set;
But bonnie feet an' braw feet sits in the kitchen neuk."
"What's that ye say?" said the prince
"Oh," says the henwife, "would ye mind what a feel bird says?"
But the prince said, "Sing that again, bonnie birdie."
So the bird sings:
"Clippit feet an' paret taes is on the saidle set;
But bonnie feet an' braw feet sits in the kitchen neuk."
The prince turned his horse and rode home, and went straight to his father's kitchen, and there sat Rashin-Coatie. He kent her at once, she was so bonnie; and when she tried on the shoe it fitted her, and so the prince married Rashin-Coatie, and they lived happy, and built a house for the red calf, who had been so kind to her.
Douglad, George. Scottish Fairy and Folk Tales.London: Walter Scott Publishing Co., 1901.