"a chopper, cutter," perhaps also "one who makes hacking tools," early 13c. (as a surname), agent noun from hack, v.1. Meaning "one who gains unauthorized access to computer records" is attested by 1983, agent noun from hack, v.2. Said to be from slightly earlier tech slang sense of "one who works like a hack at writing and experimenting with software, one who enjoys computer programming for its own sake," 1976, reputedly a usage that evolved at Massachusetts Institute of Technology (however an MIT student from the late 1960s recalls hack (n.) being used then and there in the general sense of "creative prank," which clouds its sense connection with the "writing for hire" word, and there may be a source or an influence here in hack, v.1).