Many happy returns!

[Hayhoe]

Why do people say 'Many happy returns' on someone's birthday? Is it a reference to all the unwanted presents they'll be taking back?

[Quizmonster]

"Many happy returns of the day" is really the phrase in its entirety...ie "I hope you have many more birthdays." But, what the hey! If it means returning presents, too, then so be it.

[jocook17]

i thought it meant returns as in returns on investments, though not particularly money investments, more returns on good deeds and good behaviour etc, that what goes aroung comes around and you deserve rewards because you are good