petrous (adj.)

c. 1300 (perhaps c. 1200 as a surname), from Old French lamproie "lamprey" (12c.), from Medieval Latin lampreda, from Late Latin lampetra "lamprey," a word of uncertain origin, usually explained as literally "lick-rock," from Latin lambere "to lick" (see lap (v.1)) + petra "rock" (see petrous), but this might be folk etymology. The animals attach themselves with sucker-like mouths.

biennial garden-herb, originally from the eastern Mediterranean; its aromatic leaves are used for flavoring and as a garnish; late 14c., a merger of Old English petersilie and Old French peresil (13c., Modern French persil), both from Medieval Latin petrosilium, an unexplained alteration of Latin petroselinum, from Greek petroselinon "rock-parsley," from petros "rock, stone" (see petrous) + selinon "celery" (see celery).