1766, from Mod.L.
masturbationem, from L.
masturbatus, pp. of
masturbari, altered (probably by influence of
turbare "to stir up") from
*manstuprare, from
manu, abl. of
manus "hand" (see
manual) +
stuprare "defile" (oneself), from
stuprum "defilement, dishonor," related to
stupere "to be stunned, stupefied" (see
stupid). Earlier
Onanism (q.v.). The verb
masturbate is first recorded 1857.