'petrous' originates from Latin, specifically the word 'petrosus', where 'petra' (from Greek) meant 'rock'.

'petrous' came into English via Latin 'petrosus' (and ultimately from Greek 'petra') and was adopted into scientific and anatomical usage in post-medieval English.

Initially it meant 'rocky' or 'full of rock', and over time the meaning has remained largely the same while gaining a specialized anatomical sense referring to the petrous part of the temporal bone.