cam (n.1)

1708, "vaulted building; arched roof or ceiling," from Latin camera "a vault, vaulted room" (source also of Italian camera, Spanish camara, French chambre), from Greek kamara "vaulted chamber, anything with an arched cover," which is of uncertain origin. A doublet of chamber. Old Church Slavonic komora, Lithuanian kamara, Old Irish camra all are borrowings from Latin.

The word also was used from early 18c. as a short form of Modern Latin camera obscura "dark chamber" (a black box with a lens that could project images of external objects), contrasted with camera lucida (c. 1750, Latin for "light chamber"), which uses prisms to produce an image of a distant object on paper beneath the instrument which can be traced.

This sense was expanded to become the word for "picture-taking device used by photographers" (the thing a modification of the camera obscura) when modern photography began c. 1840. The word was extended to television filming devices from 1928. Camera-shy is attested from 1890. Camera-man is from 1908.

Proto-Indo-European root meaning "tooth, nail." 

It forms all or part of: cam (n.1) "projecting part of a rotating machinery;" comb; gem; oakum; unkempt.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit jambha-s "tooth;" Greek gomphos "peg, bolt, nail; a molar tooth;" Albanian dhemb "tooth;" Old English camb "comb."