know whereof one speaks

to know well the subject that one is speaking about. You are wrong! You do not know whereof you speak. He simply doesn't know whereof he speaks.

Name	Pronounced	Usage
Hilbert	HIL-bert	German
Ichirou	ee-chee-ṙo:	Japanese
Benjaminas	-	Lithuanian
Tajeddigt	-	Northern African, Berber
Maritta	MAH-reet-tah	Finnish
Mahmood	-	Arabic