Did you
know?
off the wall
The first reference to this phrase appeared in 1953. The originating metaphor is unknown, but it most likely refers to some sport, a
racquet-sport like squash where a ball may literally be played off the wall.
To say that a person (or an idea) is "off the wall" means that he (or it) is wild, crazy, or eccentric.
This effect must be quite common in English history, we've got lots of synonyms:
absurd, ape, barmy, batty, bizarre, berserk, bonkers, cockeyed, cracked, crackpot, crazed, cuckoo, daft, delirious, demented, deranged, dingy, dippy, eccentric, erratic, flaky, flipped, flipped out, freaked out, fruity, goofy, half-baked, harebrained, haywire, idiotic, inane, insane, kooky, lunatic, loco, loony, ludicrous, mad, maniacal, mental, moonstruck, nonsensical, odd, nuts, nutty, peculiar, potty, preposterous, potty, psycho, screw loose, screwball, screwy, silly, touched, unbalanced, unglued, unhinged, unzipped, wacky, whacko, weird
You'll also hear: He's "one beer short of a sixpack" or "one sandwich short of a picnic"