A fork of Rural Dictionary
An expression pretty much meaning "believe me", only with an unnecessary "you" inserted in the middle.
That was a hard test, believe you me.
Scholars maintain that the Mayans through translation of their sun dials and all of their wise worldly knowledge used to say believe you me. The "you" being their god of sun who is all powerful and involved and responsible for everything.
I'm only funny spontaneously, believe you me!