What is the meaning of the word "wag"?

Definitions:

A humorous or witty person; a joker. NOUN
- The class wag always had a funny comment to make.
A rapid movement back and forth or up and down. NOUN
- With a wag of its tail, the dog showed its happiness.
To move a finger or other body part from side to side, often as a sign of disapproval or admonishment. VERB
- She wagged her finger at the children to indicate they should be quiet.
To move or cause to move rapidly back and forth or up and down. VERB
- The dog wags its tail excitedly when its owner comes home.
To talk or gossip, especially in a frivolous or garrulous manner. VERB
- The neighbors wagged about the latest scandal in town.