Brewer's: B

stands for 300. Scit B. trecentum sibi cognatum retinère. And, again, Et B. trecentum per se retinere videtur. But with a line above, it denotes 3,000.

For Becarre and Bemol (French for B sharp and B flat), see Becarre.

Marked with a B

(French), i.e. a poor thing. In the French language almost all personal defects begin with the letter B; e.g. bigle (squint-eyed), borgne (one-eyed), bossu (humpty), boiteux (lame), etc.

Not to know B from a battledoor.

To be quite illiterate, not to know even his letters. Miege tells us that hornbooks used to be called battledoors. The phrase might therefore originally mean not to know the B of, from, or out of, your hornbook. But its more general meaning is “not able to distinguish one letter from another.”

“He knoweth not a B from a battledoore.” —Howell; English Proverbs.

“Distinguish a B from a battledore.” —Dekker: Guls Hornebook.

I know B from a Bull's foot.

Similar to the proverb, “I know a hawk from a hernshaw.” (See Hawk.) The bull's parted hoof somewhat resembles a B.

“There were members who scarcely knew B from a bull's foot.” — Brackenbridge: Modern Chivalry.

Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894

B. C.