Word Origin & History
English agent noun ending, corresponding to L. -or. In native words it represents O.E. -ere (O.Northumbrian also -are) "man who has to do with," from W.Gmc. *-ari (cf. Ger. -er, Swed. -are, Dan. -ere), from P.Gmc. *-arjoz. Some believe this root is identical with, and perhaps a borrowing of, Latin -arius.
In words of Latin origin, verbs derived from pp. stems of Latin ones (including most verbs in -ate) usually take the Latin ending -or, as do Latin verbs that passed through French (e.g. governor), but there are many exceptions (eraser, laborer, promoter, deserter, sailor, bachelor), some of which were conformed from L. to Eng. in late M.E. The use of -or and -ee in legal language (e.g. 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 both a professional and non-professional sense (e.g. advisor/adviser, conductor/conducter, incubator/incubater, elevator/elevater).
comparative suffix, from O.E. -ra, -re, from P.Gmc. *-izon, *-ozon (cf. Goth. -iza, O.S. -iro, O.N. -ri), originally also with umlaut change in stem, but this was mostly lost in O.E. by historical times and has now vanished (except better and elder).
suffix used to make jocular or familiar formations from common or proper names (soccer
being one), first attested 1860s, English schoolboy slang, "Introduced from Rugby School into Oxford University slang, orig. at University College, in Michaelmas Term, 1875" [OED, with unusual precision].