not know B from a battledore

To be really stupid, or perhaps illiterate. The now-outdated term "battledore" was often used in reference to a children's primer. It was likely used in this phrase simply for the sake of alliteration. How do you manage to burn pasta? It's like you don't know B from a battledore.

Common Names:

Name	Pronounced	Usage
Harsha	-	Indian, Kannada, Telugu, Sanskrit
Cherish	CHER-ish	English
Yeong-Ja	yung-jah	Korean
Benjamin	['bendʒəmin]
ArtŪRas	-	Lithuanian
Wynn	WIN	Welsh