baptism (n.) Look up baptism at Dictionary.com
c.1300, bapteme, from Old French batesme, bapteme (11c., Modern French baptême), from Latin baptismus, from Greek baptismos, noun of action from baptizein (see baptize). The -s- restored in later 14c.

Figurative sense is from late 14c. The Anglo-Saxons used fulluht in this sense (John the Baptist was Iohannes se Fulluhtere). Phrase baptism of fire "a soldier's first experience of battle" (1857) translates French baptême de feu; the phrase originally was ecclesiastical Greek baptisma pyros and meant "the grace of the Holy Spirit as imparted through baptism." Later it was used of martyrdom, especially by burning.