1520s, "to be in agreement, to be in harmony with," from M.L. correspondere
, from cor-
) "together, with each other" + respondere
"to answer" (see respond
). Originally in M.L. of two things in mutual action, but by later M.L. it could be used of one thing only. In English, sense of "to be similar" (to) is from 1640s; that of "to hold communication with" is from c.1600; specifically "to communicate by means of letters" from 1640s (in mid-18c. it also could mean "have sex").