-er

a suffix used in forming nouns designating persons from the object of their occupation or labor (hatter; tiler; tinner; moonshiner), or from their place of origin or abode (icelander; southerner; villager), or designating either persons or things from some special characteristic or circ-mstance (six-footer; three-master; teetotaler; fiver; tenner).
a suffix serving as the regular english formative of agent nouns, being attached to verbs of any origin (bearer; creeper; employer; harvester; teacher; theorizer).
-er2
a noun suffix occurring in loanwords from french in the middle english period, most often names of occupations (archer; butcher; butler; carpenter; grocer; mariner; officer), but also other nouns (corner; danger; primer). some historical instances of this suffix, as in banker or gardener, where the base is a recognizable modern english word, are now indistinguishable from denominal formations with -er1, as miller or potter.
origin
-er3
a termination of nouns denoting action or process: dinner; rejoinder; remainder; trover .
origin
-er4
a suffix regularly used in forming the comparative degree of adjectives: harder; smaller .
origin
-er5
a suffix regularly used in forming the comparative degree of adverbs: faster .
origin
-er6
a formal element appearing in verbs having frequentative meaning: flicker; flutter; shiver; shudder .
origin
-er7
a suffix that creates informal or jocular mutations of more neutral words, which are typically clipped to a single syllable if polysyllabic, before application of the suffix, and which sometimes undergo other phonetic alterations: bed-sitter; footer; fresher; rugger . most words formed thus have been limited to english public-school and university slang; few, if any, have become current in north america, with the exception of soccer, which has also lost its earlier informal character.
origin
-er1
suffix
a person or thing that performs a specified action reader, decanter, lighter
a person engaged in a profession, occupation, etc writer, baker, bootlegger
a native or inhabitant of islander, londoner, villager
a person or thing having a certain characteristic newcomer, double-decker, fiver
word origin
-er2
suffix
forming the comparative degree of adjectives (deeper, freer, sunnier, etc) and adverbs (faster, slower, etc)
word origin
-er
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 p-ssed 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).
-er
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).
-er
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].