1530s, "a running (usually at full speed), a course" (especially of the sun, etc., across the sky), from French carriere "road, racecourse" (16c.), from Old Provençal or Italian carriera, from Vulgar Latin *(via) cararia "carriage (road), track for wheeled vehicles," from Latin carrus "chariot" (see car). Sense of "general course of action or movement" is from 1590s, hence "course of one's public or professional life" (1803).
1590s, "to charge at a tournament," from career (n.). The meaning "move rapidly, run at full speed" (1640s) is from the image of a horse "passing a career" on the jousting field, etc. Related: Careered; careering.