How does the house elves clothes rule work and why?

Question

We know from the question "How did the house elves start serving wizards?" that it is not sure when was house elves enslaved, so we probably don't know the evolution of the rule in the past.

But the rule is pretty strange, right? I mean, why clothes? Why not any gift for example?

I see more options here:

1. House elves made the rule by themselves in the long past (and the rule is powerful because generations of house elves believe in it) – it is in their heads, that is why Dobby could be freed in the little controversy way, he just persuaded himself (Malfoy didn't want to give him sock, it wasn't even his).

2. The rule is magically made by the original slave master, the rules are made by him (then the question again is: Why clothes? How does it work exactly? What could be his intention?)

3. The rule is something from nature, house elves are born with it. That would mean that they were born (or created?) to serve wizards. Which leads to other questions: Was it always like that? Clothes aren't exactly nature invention. Is there any other way to free them (maybe clothes are just subset of possible ways)?

To sum up

How does the rule work? Is it some of these options? Is there another way to free a house elf?

Answer 1

The rule isn't clothes per se - it's ownership. Clothes specifically were picked to demonstrate servitude because they are the most visible and noticeable objects to observers.

I explain the rules pretty clearly here (mostly fact, some headcanon). I feel that the impossibility of house-elves to own clothes shows that they are subject to someone else's whims and are not there own property. (Interestingly, this was how ancient Jewish law viewed it as well - a slave was not allowed to own anything of any kind, to demonstrate servitude.)

Why clothes? There isn't much evidence, but we do have one quote from Dobby: COS CH 21:

He blew his nose on a corner of the filthy pillowcase he wore, looking so pathetic that Harry felt his anger ebb away in spite of himself. “Why d’you wear that thing, Dobby?” he asked curiously. “This, sir?” said Dobby, plucking at the pillowcase. “ ’Tis a mark of the house-elf’s enslavement, sir.

Clothes are immediately observable which leads to public knowledge. This also explains why Dobby wears all his clothes at once - it demonstrates he's a free elf:

GOF Ch. 21:

When Dobby had worked for the Malfoys, he had always worn the same filthy old pillowcase. Now, however, he was wearing the strangest assortment of garments Harry had ever seen; he had done an even worse job of dressing himself than the wizards at the World Cup. He was wearing a tea cozy for a hat, on which he had pinned a number of bright badges; a tie patterned with horseshoes over a bare chest, a pair of what looked like children’s soccer shorts, and odd socks. One of these, Harry saw, was the black one Harry had removed from his own foot and tricked Mr. Malfoy into giving Dobby, thereby setting Dobby free. The other was covered in pink and orange stripes.

Conversely, this explains why

[No other elves] will clean Gryffindor Tower any more, not with the hats and socks hidden everywhere, they finds them insulting, sir. Dobby does it all himself, sir.

Since the only way to go free is with a public display of private clothes, peer pressure of a sort causes house-elves to feel embarrassed to go free. (That's why Winky stuck to her old garment - unlike Dobby, she was embarassed.)