House-elf slavning predated Foundations of Hogwarts (ca 990 e.Kr.) och fördes till Hogwarts av Helga Hufflepuff, (även om hon inte började enslavementet.)
Detta var tydligast av J K Rowling i en Pottercast-intervju. 1
J.K. Rowling (JKR): This had better not be about House-Elves.
Melissa Anelli (MA): Jo, it is! I'm sorry! It is.
Sue Upton (SU): Hey, Jo! Hello!
John Noe (JN): Hey, Jo!
MA: Hiiiii!
JKR: What? House-Elves? Go on then.
MA: Still. Still. They are still arguing about this, and I'm sick of it, and we need you to answer it so bad.
JN: What I'm telling Sue is that, if she remembered from when we talked about this in New York1, Jo said that Helga Hufflepuff was a plantation owner of the House-Elves ....
SU: Yeah, but she gave them refuge! Refuge! R-E...
JKR: Refuge.
SU: She didn't enslave them.
JKR: Yeah, it's a complicated issue, you know? I would say that Hufflepuff gave... Hufflepuff did what was the most moral thing to do at that time, and we are talking about over a thousand years ago. So that would be to give them good conditions of work. There was no kind of activism there, so no one's gonna say, "Here's an idea. Let's, let's free them. Let's, uh, let's pay them." It was just "well, we'll bring them somewhere that they can work and not be abused."
SU: See? She did not go around with like a whip and say "Yaaah! You must work in the kitchens!" you know?
JKR: Definitely not, no. That would not be... No, no. Definitely not.
SU: See? Woohoo! Thank you, Jo.
(Anelli, Melissa, John Noe and Sue Upton. "PotterCast Interviews J.K. Rowling, part one." PotterCast #130, 17 December 2007. (transcript))
Det finns för närvarande inte mer information än det.
1: Detta avslöjades tidigare av J K Rowling under Open Book Tour på Carnegie Hall i en konversation med Leaky Cauldron. Inget transkript eller inspelning existerar så vitt jag vet, men det pratades om i Pottercast # 122 (hoppa till 12:55) ( transkription )
( sammanfattade av Accio-Quote som " Helga Hufflepuff erbjöd husälven tillflykt på Hogwarts , även om förhållandena var slavliknande, om det var lite snyggare än någon annanstans. ")