Etymology: Middle English, pair, bond, from Anglo-French cuple, from Latin copula bond, from co- + apere to fasten — more at apt
Date: 13th century
a. two persons married, engaged, or otherwise romantically paired
b. two persons paired together
2. pair, brace
3. something that joins or links two things together: as
a. two equal and opposite forces that act along parallel lines
b. a pair of substances that in contact with an electrolyte participate in a transfer of electrons which causes an electric current to flow
4. an indefinite small number ; few <a couple of days ago> • coupledom noun II. verb (coupled; coupling) Date: 13th century transitive verb 1. a. to connect for consideration together b. to join for combined effect 2. a. to fasten together ; link b. to bring (two electric circuits) into such close proximity as to permit mutual influence 3. to join in marriage or sexual union intransitive verb 1. to unite in sexual union 2. join 3. to unite chemically III. adjective Date: 1924 two; also few — used with a <a couple drinks> Usage: The adjective use of a couple, without of, has been called nonstandard, but it is not. In both British and American English it is standard before a word (as more or less) indicating degree <a couple more examples of Middle English writing — Charles Barber>. Its use before an ordinary plural noun is an Americanism, common in speech and in writing that is not meant to be formal or elevated <the first couple chapters are pretty good — E. B. White (letter)> <still operated a couple wagons for hire — Garrison Keillor>. It is most frequently used with periods of time <a couple weeks> and numbers <a couple hundred> <a couple dozen>.
New Collegiate Dictionary. 2001.