An phrase coined by "TrainWreckTV" from
Twitch.
It is an alternative for "I will keep it
real with you".
TrainWreckTV (Tyler) is very candid with his viewers about his past and present, and he is not hiding things, and whenever he has a moment when he is going to tell
something sensitive or very honest, he is saying "I will keep it buck fifty with you"
"I will keep it buck fifty with you, that new
car that you bought is putrid"
"I will keep it buck fifty with you, I have some
money problems"