swear on (one's) mother's grave

To make a very serious, solemn pledge, especially that one is telling the truth. Janet has sworn on her mother's grave that she wasn't the one to betray me, and I believe her. I swear on my mother's grave that if I have a chance to help your campaign, I will.

Common Names:

Name	Pronounced	Usage
Latanya	-	African American
Persephone	pər-SEF-ə-nee (English)	Greek Mythology
Kyros	-	Ancient Greek, Biblical Greek
ClÍOdhna	KLEE-u-na	Irish, Irish Mythology
Joseph	['dʒəuzif]
OcÉAne	o-se-AHN	French