Origin of overboard
- to be extremely enthusiastic
- to go to extremes
"over the side of a ship," Old English ofor bord, from over + bord "side of a ship" (see board (n.2)). Figurative sense of "excessively, beyond one's means" (especially in phrase go overboard) first attested 1931 in Damon Runyon.
Show excessive enthusiasm, act in an excessive way. For example, It's easy to go overboard with a new stock offering, or She really went overboard, hiring the most expensive caterer. [Mid-1900s]
see go overboard.