What does "pū" on itself literally translate to? "With you"? is "ʻAi pū au" "I eat with you"?
Pu actually has many literal translations, but the ones that you are interested in is as follows: "(part.) definition - Together, entirely, completely, also with, together with."
It is often used colloquially as a form of good-bye, or perhaps in an email or written correspondence as well. It means "God with you," and it that form may be translated as a blessing.