The explanation I heard is that it is derived from "debased". As in the opposite of debased is "based". I don't think this is strictly correct[0], but it does g

The explanation I heard is that it is derived from "debased". As in the opposite of debased is "based". I don't think this is strictly correct[0], but it does give a good definition. [0]: I think the original term comes from street slang and has something to do with freebase cocaine and evolved from there through various online communities.