"the Anointed," synonymous with and translating to Greek  Hebrew mashiah (see messiah), a title given to Jesus of Nazareth; Old English crist (by 830, perhaps 675), from Latin Christus, from Greek khristos "the anointed," noun use of verbal adjective of khriein "to rub, anoint" (from PIE root *ghrei- "to rub").

In the primitive Church it was a title, and used with the definite article, but from an early period it was used without it and regarded as part of the proper name of Jesus. It was treated as a proper name in Old English, but not regularly capitalized until 17c. Pronunciation with long -i- is result of Irish missionary work in England, 7c.-8c. The ch- form, regular since c. 1500 in English, was rare before. Capitalization of the word begins 14c. but is not fixed until 17c.  The Latin term drove out Old English Hæland "healer, savior," as the preferred descriptive term for Jesus.

As an oath or strong exclamation (of surprise, dismay, etc.), attested by 1748. The 17c. mystical sect of the Familists edged it toward a verb with Christed "made one with Christ." Christ-child "Jesus as a baby" (1842) translates German Christkind.

c. 1200, "to baptize into the Christian church," from Old English cristnian "to baptize," literally "to make Christian," from cristen "Christian" (see Christian). Especially to baptize and name as an infant, hence "give a name to at baptism" (mid-15c.) and the general sense of "give a name to" anything, without reference to baptism (1530s). Related: Christened; christening.

Old English cristendom "Christianity, state of being a Christian, profession of faith in Christ by baptism," from cristen (see Christian) + -dom, suffix of condition or quality. The native formation, crowded out by Latinate Christianity except in the sense of "lands where Christianity is the dominant religion" (late 14c.). Similar formations are found in Scandinavian languages.

1570s, "Christianity, the Christian religion," from Christian + -ism. Obsolete, but revived or recoined c. 2004 in reference to politicized fundamentalist Christianity in the U.S. Related: Christianist.

c. 1300, cristente, "Christians as a whole; state of being a Christian; the religion founded by Jesus," from Old French crestienté "Christendom; spiritual authority; baptism" (Modern French chrétienté), from Church Latin christianitatem (nominative christianitas), noun of state from christianus (see Christian). Gradually respelled to conform with Latin. Christendom is the older word for it. Old English also had cristennes.

1590s, from Christian + -ize. Originally intransitive ("follow or profess Christianity") as well as transitive ("make Christian, convert to Christianity"). Related: Christianized; christianizing; christianization.

ghrēi-, Proto-Indo-European root meaning "to rub." 

It forms all or part of: chrism; Christ; christen; Christian; Christmas; cream; grime; grisly; Kriss Kringle.

It is the hypothetical source of/evidence for its existence is provided by: Greek khriein "to anoint, besmear;" Lithuanian grieju, grieti "to skim the cream off;" Old English grima "mask, helmet, ghost," Middle Low German greme "dirt."

by 1807 as "after the lifetime of Christ," from post- + Christ + -ian; by 1929 as "after the decline or rejection of Christianity," from Christian.