mid-15c., "ample, profuse," from Old French frequent, or directly from Latin frequentem (nominative frequens) "often, regular, repeated; in great numbers, crowded, numerous, filled, full, populous," which is of uncertain origin. Watkins says probably from PIE *bhrekw- "to cram together," and compares Greek phrassein "to fence in," Latin farcire "to cram." Meaning "common, usual" is from 1530s; that of "happening at short intervals, often recurring" is from c.1600.

late 15c., "visit or associate with," from Old French frequenter "attend frequently; assemble, gather together," from Latin frequentare "visit regularly; do frequently, repeat; assemble in throngs," from frequentem (see frequent, adj.). Meaning "visit often" is from 1550s. Related: Frequented; frequenter; frequenting.