B & L
Battles and Leaders of the Civil War. First published by the Century Company in 1888 and republished several times since.
Capt.
Captain.
Co.
Company or County, depending on context.
Col.
Colonel.
Corduroy
Normally a ribbed cotton trouser material, but in a Civil War context a method of building or repairing roads in boggy areas using trimmed tree trunks.
Corp. or Cpl.
Corporal.
Genl.
General.
Lieut. or Lt.
Lieutenant.
O.R.
Official Records of the War of Rebellion. Published by the U.S. War department in 1880 in 128 volumes.
Old Dominion
Another name for the state of Virginia