I recently listened to a podcast that mentioned a "waxing gibbous moon," and wondered about the definition and etymology.
In astronomical terms, gibbous moons precede and follow the full moon. The etymology is from Middle English, from Latin gibbus (“humped, hunched”), probably cognate with cubō (“bend oneself, lie down”), Italian gobba (“humpback”), Greek κύφος (kýfos, “humpback, bent”), κύβος (kývos, “cube, vertebra”).
So the gibbous moon is "humped" but it's not the same as the crescent moon, which occurs in the other half of the cycle, around the new moon.
In medical terms, a gibbus deformity is a sharp angulation of the spine (image via), slightly different from the more gradual deformity of conventional kyphosis.