-er

CIDE DICTIONARY

-er,  

•  .
•  The termination of many English words, denoting the agent; -- applied either to men or things; as in hater, farmer, heater, grater. At the end of names of places, -er signifies a man of the place; as, Londoner, i. e., London man.  [1913 Webster]
•  A suffix used to form the comparative degree of adjectives and adverbs; as, warmer, sooner, lat(e)er, earl(y)ier.  [1913 Webster]

OXFORD DICTIONARY

-er, suffix forming nouns from nouns, adjectives, and many verbs, denoting:
1 a person, animal, or thing that performs a specified action or activity (cobbler; lover; executioner; poker; computer; eye-opener).
2 a person or thing that has a specified attribute or form (foreigner; four-wheeler; second-rater).
3 a person concerned with a specified thing or subject (hatter; geographer).
4 a person belonging to a specified place or group (villager; New Zealander; sixth-former).

-er, suffix forming the comparative of adjectives (wider; hotter) and adverbs (faster).

-er, suffix used in slang formations usu. distorting the root word (rugger; soccer).

-er, suffix forming iterative and frequentative verbs (blunder; glimmer; twitter).

-er, suffix.
1 forming nouns and adjectives through OF or AF, corresponding to: a L -aris (sampler) (cf. -AR(1)). b L -arius, -arium (butler; carpenter; danger). c (through OF -e{uuml}re) L -atura or (through OF -e{ouml}r) L -atorium (see COUNTER(1), FRITTER(2)).
2 = -OR.

-er, suffix esp. Law forming nouns denoting verbal action or a document effecting this (cesser; disclaimer; misnomer).

Usage

The same ending occurs in dinner and supper.

Etymology

AF infin. ending of verbs