The etymology of the Latin verb "masturbari" is vexed. It has been argued that it is a compound of "turbare" 'agitate' and "mas" 'male', in an otherwise unattested usage for 'penis'. One traditional view sees "man(u)-" 'hand' with an altered form of "stuprare" 'to defile, commit a sexual wrong against'. Calvert Watkins proposed that it derives from a Proto-Indo-European root meaning 'marrow, brain', since ancient medical writers believed that semen descended from the brain through the bones; if this is correct, the word "turbare" may still have influenced the formation in Latin.