c. 1400, in anatomy, "very hard, dense," from Old French petros (Modern French petreux) and directly from Latin petrosus "stony," from petra "rock," from Greek petra "rock, cliff, ledge, shelf of rock, rocky ridge," a word of unknown etymology (Beekes says it is "probably Pre-Greek"). Used of certain bones, especially of parts of the temporal bone.

surname, attested from late 12c., from Old French Piers, nominative of proper name Pierre (see Peter) .

familiar form of masc. proper name Peter. For Pete's sake is attested from 1903 in a list of children's expressions published in Massachusetts, probably a euphemistic use of the disciple's name in place of Christ; as an exclamation or quasi-oath, Peter! was in use 14c., but this likely is not the source of the modern use.

Modern French form of the masc. proper name represented in Modern English by Peter (q.v.). The city in South Dakota, U.S., was named for Pierre Chouteau (1789-1865) who set up an Indian trading post there in 1837.

common Old French form of masc. proper name Peter (q.v.).