Origin and history of tailer

c. 1500, tailen, "follow at the tail of, straggle after," from tail (n.1). It is attested from 1520s in the sense of "attach to the tail;" by 1781 as "move or extend in a way suggestive of a tail."

It can mean both "furnish with a tail" (1817) and "remove the tail or end of" (1794). The meaning "follow secretly" is U.S. colloquial, 1907; earlier it meant "follow or drive" sheep or cattle. To tail off "diminish" is attested from 1854; as a noun by 1975. Related: Tailed (attested from c. 1300 as "having a tail or tail-like appendage"); tailing.