From Latin crux (cross, wooden frame for execution), from the Proto-Indo-European *(s)ker- (to turn, to bend). Doublet of cross.

Borrowed from Latin crux or English crux, in the phrase crux interpretum.

From Proto-Indo-European *(s)ker- (to turn, to bend).[1] Possible cognate with Latin circus (circle) and curvus (curve).

The intermediate steps of the following borrowings are undetermined. They are organized into groups that may be from the same source.