accomplice (n.) Look up accomplice at Dictionary.com
"associate in crime," 1580s, an unetymological extension of earlier complice "an associate or confederate" (early 15c.), from Old French complice "a confederate, partner" (not in a criminal sense), from Late Latin complicem (nominative complex) "partner, confederate," from Latin complicare "to involve," literally "fold together" (see complicate). Altered perhaps on model of accomplish, etc., or by assimilation of the indefinite article in a complice.