-er

from The Collaborative International Dictionary of English v.0.48

Er \Er\ n.
   the chemical symbol for {erbium}, a rare earth element. It
   has atomic number 68 and an atomic weight of 167.26.

   Syn: erbium.
        [WordNet 1.5 +PJC]

from The Collaborative International Dictionary of English v.0.48

-er \-er\
   .

   1. [AS. -ere; akin to L. -arius.] 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]

   2. [AS. -ra; akin to G. -er, Icel. -are, -re, Goth. -iza,
      -?za, L. -ior, Gr. ?, Skr. -[imac]yas.] A suffix used to
      form the comparative degree of adjectives and adverbs; as,
      warmer, sooner, lat(e)er, earl(y)ier.
      [1913 Webster]

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

ER
       Enterprise Replication (IDS, Informix, DB)

from V.E.R.A. -- Virtual Entity of Relevant Acronyms (June 2006)

ER
       Externer Rechner (T-Online)

from Hitchcock's Bible Names Dictionary (late 1800's)

Er, watchman