promoter n.

late 14c., promoten, "to advance (someone) to a higher grade or office, exalt or raise to a higher post or position," from Old French promoter and directly from Latin promotus, past participle of promovere "move forward, advance; cause to advance, push onward; bring to light, reveal," from pro "forward" (see pro-) + movere "to move" (from PIE root *meue- "to push away").

General sense of "to further the growth or progress of (anything)" is from early 15c. In late Middle English and early Modern English also promove, from the Latin verb. Related: Promoted; promoting.

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).