Etymology for 「デブ」
 

Hi people. This is just a quick little question I had.

Okay, so デブ means "fat" in Japanese. I asked my Japanese teacher about it, but he didn't know what it meant, so that must mean it's slang, right? That got me thinking about the etymology of the word. It sounds like it comes from "Deb", which I'm guessing is maybe some kind of store for obese woman or something. I'm curious as to where this word came from. Does anyone know?

Thank you!!

EDIT: FYI, my Japanese teacher is from Japan.

広辞苑（A Japanese dictionary)
でぶ　肥えていること、また、その人をあざけっていう 語

Hi. I think every Japanese native knows the word.
It is not slang, but colloquial and a dirty-word, like "fat-ass".

I strongly believe that your teacher misunderstood what you said,
or he/she pretended to not-knowing, because he/she didn't want you to learn a dirty-Japanese-word.

Oh, you're asking the etymology?
Sorry. I don't know.

edit) The mighty Wikipedia says that it comes from the adjective でっぷり.
In Edo-era, でっぷり　became でぶでぶ, then became でぶ.

デブ - Wikipedia

デブ is not a nice word, but it is not a dirty word, either.

I assume your teacher did not want you to learn the word. My teacher used to deny that plain form Japanese existed.

Haha, you have a really horrible teacher! It's impossible to speak Japanese without the plain form (as you well know)!