"overly-zealous Christian," 1910, originally sailors' slang, from Christ + -er (1).
Entries linking to christer
Christ n.
"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.
-er 1
English agent noun ending, corresponding to Latin -or. In native words it represents Old English -ere (Old Northumbrian also -are) "man who has to do with," from Proto-Germanic *-ari (cognates: German -er, Swedish -are, Danish -ere), from Proto-Germanic *-arjoz. Some believe this root is identical with, and perhaps a borrowing of, Latin -arius (see -ary).
Generally used with native Germanic words. In words of Latin origin, verbs derived from past participle stems of Latin ones (including most verbs in -ate) usually take the Latin ending -or, as do Latin verbs that passed through French (such as governor); but there are many exceptions (eraser, laborer, promoter, deserter; sailor, bachelor), some of which were conformed from Latin to English in late Middle English.
The use of -or and -ee in legal language (such as lessor/lessee) to distinguish actors and recipients of action has given the -or ending a tinge of professionalism, and this makes it useful in doubling words that have a professional and a non-professional sense (such as advisor/adviser, conductor/conducter, incubator/incubater, elevator/elevater).