Yours, Etc.: Origins and Uses of 8 Sign-Offs
Old English flocc "a group of persons, company, troop," related to Old Norse flokkr "crowd, troop, band," Middle Low German vlocke "crowd, flock (of sheep);" not found in other Germanic languages; perhaps related to folc "people," but the metathesis would have been unusual for Old English.
Extended c.1200 to "a number of animals of one kind moving or feeding together;" of domestic animals c.1300. Transferred to bodies of Christians, in relation to Christ or their local pastor, from mid-14c.
"tuft of wool," mid-13c., probably from Old French floc, from Latin floccus "flock of wool, lock of hair."
"gather, congregate," c.1300, from flock (n.). Related: Flocked; flocking.