The Collaborative International Dictionary of English v.0.48:
Wag \Wag\, v. t. [imp. & p. p. Wagged; p. pr. & vb. n.
Wagging.] [OE. waggen; probably of Scand. origin; cf. Sw.
vagga to rock a cradle, vagga cradle, Icel. vagga, Dan.
vugge; akin to AS. wagian to move, wag, wegan to bear, carry,
G. & D. bewegen to move, and E. weigh. [root]136. See
To move one way and the other with quick turns; to shake to
and fro; to move vibratingly; to cause to vibrate, as a part
of the body; as, to wag the head.
No discerner durst wag his tongue in censure. --Shak.
Every one that passeth thereby shall be astonished, and
wag his head. --Jer. xviii.
Note: Wag expresses specifically the motion of the head and
body used in buffoonery, mirth, derision, sport, and