(wag) v. wagged, wag·ging v.t.
1. To cause to move lightly and quickly from side to side or up and down; oscillate; swing: The dog wags its tail.
2. To move (the tongue) in talking.
—v.i.
3. To move lightly and quickly from side to side or up and down.
4. To move busily in animated talk or gossip: said of the tongue.
5. To proceed at a regular pace: Life wags on.
6. To waddle.
7. Brit. Slang To play truant.
—noun The act or motion of wagging: a wag of the head. [ME waggen, prob. <Scand. Cf. Sw. vagga rock a cradle. Akin to OE wagian oscillate.]

(wag) noun
A droll or humorous fellow; a wit; joker. [Short for obs. waghalter <WAG¹ + HALTER¹]