means A short label, marker, or piece of identifying information attached to something — or, as a verb, to add such a label, or to touch someone in the game of the same name.

from The childhood game and the label feel like strangers, but English knotted them together centuries ago. 'Tag' for a hanging scrap or dangling end appeared in late Middle English, likely from a Scandinavian source related to words for a tuft or point — think of the little metal tip on a shoelace, the aglet, which carries the same idea of a small thing fixed to the end of a bigger thing. From 'dangling bit' the word stretched naturally to 'attached label,' then in the modern era to digital labels and #hashtags. The game 'tag' is the odder cousin: its sense of touching or catching probably grew from the same 'to attach, to make contact' notion, though the exact path is murky.