The phrase “Hail fellow well met” is an archaic reference to someone who is always cheerful but who is perhaps overdoing his or her enthusiasm.
The expression began pleasantly enough as the medieval Scottish greeting hail, which is how the Scots pronounced heal.
“Hale fellow” meant “health to you, friend.”
In the sixteenth century, the expression became associated with the words buddy or mate. “Well met!” followed, meaning, “It’s good to meet you!”
The two expressions became combined in a fuller phrase, “Hail-fellow-well-met,” in the late sixteenth century and is used today to suggest that a person’s exuberance is perhaps exaggerated.