tag (n.1) Look up tag at Dictionary.com
"small hanging piece from a garment," c.1400, perhaps from a Scandinavian source (cf. Norwegian tagg "point, prong, barb," Swedish tagg "prickle, thorn," Middle Low German tagge "branch, twig, spike"); cognate with tack (n.1). Meaning "label" is first recorded 1835; sense of "automobile license plate" is recorded from 1935, originally underworld slang. Meaning "an epithet, popular designation" is recorded from 1961, hence slang verb meaning "to write graffiti in public places" (1990).
tag (n.2) Look up tag at Dictionary.com
"children's game," 1738, perhaps a variation of Scot. tig "touch, tap" (1721), probably an alteration of Middle English tek "touch, tap" (see tick (2)).
tag (v.1) Look up tag at Dictionary.com
"to furnish with a tag," mid-15c., from tag (n.1). Related: Tagged; tagging. To tag along is first recorded 1900.
tag (v.2) Look up tag at Dictionary.com
in the baseball sense, 1907, from tag (n.2); the adjective in the pro-wrestling sense is recorded from 1955.