"resident or native of London," mid-15c., from London + -er (1). Earlier (late 14c.) was Londenoys, from Anglo-French Londenois.
Entries linking to londoner
London
chief city and capital of England, Latin Londinium (Tacitus, c. 115), according to the "Cambridge Dictionary of English Place-Names," "unexplained." It is often said to be "place belonging to a man named *Londinos," a supposed Celtic personal name meaning "the wild one," "but this etymology is rejected in an emphatic footnote in Jackson 1953 (p. 308), and we have as yet nothing to put in its place" [Margaret Gelling, "Signposts to the Past: Place-Names and the History of England," Chichester, 1978]. Its mythical history is told in Layamon's "Brut" (c. 1200).
In late Old English often with -burg, -wic, or -ceaster. As an adjective, Old English had Lundenisc, but this seems to have fallen from use, and modern Londonish (1838) probably is a re-coinage. Also Londony (1884); Londonesque (1852); Londinensian (George Meredith); Londonian (1824, marked "rare" in OED).
London Bridge the children's singing game is attested from 1827. London broil "large flank steak broiled then cut in thin slices" attested 1930s, American English; London fog first attested 1785.
-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).