Logorrhea
(lah-goh-REE-uh)
Definition: The tendency to talk a lot or be chatty
Origins: I'll just make this one up: logo is Greek for 'word,' so they just stuck 'rrhea' on the end, as in diarrhea, and now it means somethings like 'word-diarrhea.' Makes sense, right?
Sentence: "Sierra was prone to logorrhea, which annoyed the more laconic Lily greatly."