-er

Webster's Dictionary of the English Language

·- -ere; akin to ·Lat. -arius.

II. -er ·- A suffix used to form the comparative degree of adjectives and adverbs; as, warmer, sooner, lat(e)er, earl(y)ier.

III. -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.