1535-45; < Latinabscessus a going away, abscess, equivalent to absced-, variant stem of abscēdere to go away, separate off, form an abscess (abs-abs- + cēdere; see cede) + -tus suffix of v. action, with -dt- > -ss-
1610s, from Latin abscessus "an abscess" (Celsus), literally "a going away," from stem of abscedere "withdraw," from ab- "away" (see ab-) + cedere "to go" (see cede). The notion is that humors "go from" the body through the pus in the swelling.