To mate; match.
Two persons or things of a kind associated; a couple; brace.
A single thing having two like or corresponding parts.
I have a pair on. – The Crofton Boys by Harriet Martineau
" One pair more or less doesn't make much difference," said Olga. – The Keeper of the Door by Ethel M. Dell
Ruby an' he'll make a han'some pair. – I Saw Three Ships and Other Winter Tales by Arthur Thomas Quiller-Couch