1846, in pathology, adjective from abscess (n.). If there is a verb abscess it would be a back-formation from this.
Entries linking to abscessed
abscess n.
in pathology, "collection of pus in some part of the body," 1610s, from Latin abscessus "an abscess" (the Latin word was used in a medical sense by Celsus), literally "a going away, departure," from the stem of abscedere "withdraw, depart, retire," from ab "off, away from" (see ab-) + cedere "to go, withdraw" (from PIE root *ked- "to go, yield"). The notion is that humors "go from" the body through the pus in the swelling.