Hm. I read a great deal and began playing games when I was quite young, so its hard to say just very my vocabulary came from, though since I've always enjoyed language heavy games I'm sure they were a big part of it.
I would bet that the old text based games like Zork and Colossal Cave as well as MUDs and MUSHes later expanded the selection of words I would commonly use, even if I may have already known their definition.
Drink the potion
I don't understand.
Swallow the potion
I don't understand.
Um, Eat the potion?
I don't understand.
Just drink the damn potion!
I don't understand.
*Finds instructions* Quaff, really? Ok, Quaff the potion.
You drink the potion.
Really game? You did that on purpose.