couple

1175–1225; (noun) Middle English < Anglo-French c(o)uple, Old French cople, cuple < Latin cōpula a tie, bond (see copula); (v.) Middle English couplen < Anglo-French co(u)pler, Old French copler, cupler < Latin copulāre (see copulate)

The phrase a couple of, meaning “a small number of; a few; several,” has been in standard use for centuries, especially with measurements of time and distance and in referring to amounts of money: They walked a couple of miles in silence. Repairs will probably cost a couple of hundred dollars. The phrase is used in all but the most formal speech and writing. The shortened phrase a couple, without of ( The gas station is a couple miles from here ), is an Americanism of recent development that occurs chiefly in informal speech or representations of speech, especially when followed by number terms (as a couple dozen eggs ) or units of measurement (as a couple years ago; a couple gallons of gas ). This use of couple (as an adjective or modifier) is still disliked by many. Without a following noun, a couple is even more informal: Jack shouldn't drive. It's clear he's had a couple. (Here the noun drinks is omitted.)
In referring to two people, couple, like many collective nouns, may take either a singular or a plural verb. Most commonly, it is construed as a plural: The couple were traveling to Texas. See also collective noun.