know the first thing about

not know the first thing about something

to not know anything about a particular subject I don't know why you're asking Rob, he doesn't know the first thing about classical music.

Name	Pronounced	Usage
Amity	AM-i-tee	English (Rare)
Artem	-	Ukrainian, Belarusian, Russian
Unathi	-	Southern African, Xhosa
Rokuro	ṙo-koo-ṙo:	Japanese
Katey	KAY-tee	English
Roos	RO:S	Dutch