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
Davina	[də'vi:nə]
Giuliana	joo-LYAH-nah	Italian
Hugues	-	French
Marisa	mah-REE-zah (Italian), mah-REE-sah (Spanish), mə-RIS-ə (English)	Italian, Spanish, Portuguese, English
Rena	-	English
Achille	a-SHEEL (French), ah-KEEL-le (Italian)	French, Italian