To swear something on one's father's grave...followed by the word "though"
Dat bitch be trippin on me...cakin' wit' dat fake ass nigga! I got both they assses! Pappy Doe!
Trans: That young lady (my girl, or ex) is messing around behind my back with a gentleman that I don't care for. That's cool. I'm gonna beat both of their asses. I swear on father's grave that this is the case!
The same as "on my momma". (See on my momma)
I swear on my mother's grave...followed by the word, "Though" or preceded by the word, "However"
Imma beat dat ass fam...mammy doe!
(However, I swear on my mother's grave, that I'm gonna kick your ass)