corsair (n.) Look up corsair at Dictionary.com
1540s, from Middle French corsaire (15c.), from Provençal cursar, Italian corsaro, from Medieval Latin cursarius "pirate," from Latin cursus "course, a running," from currere "to run" (from PIE root *kers- "to run"). Meaning of the Medieval Latin verb evolved from "course" to "journey" to "expedition" to an expedition specifically for plunder.