What does 'a couple of' mean?

Solution 1:

The main meaning and its etymology refer literally to two related persons or things. By extension a couple is used to mean “a few”, so more than two:

Couple:

late 13c., "two of the same kind or class connected or considered together," especially "a man and a woman associated together by marriage or love," from Old French cople "married couple, lovers" (12c., Modern French couple), from Latin copula "tie, connection," from PIE *ko-ap-, from *ko(m)- "together" + *ap- "to take, reach." (Etymonline)

Idiom, a couple of:

more than two, but not many, of; a small number of; a few:

• It will take a couple of days for the package to get there. A dinner party, whether for a couple of old friends or eight new acquaintances, takes nearly the same amount of effort. (Dictionary.com)

Solution 2:

Two train carriages are (individually) coupled together!