A flea. The pun is F, the initial letter, and sharp because the bite is acute. (See B Flats.)
· ·
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Entry taken from Dictionary of Phrase and Fable, edited by the Rev. E. Cobham Brewer, LL.D. and revised in 1895.
· 
· 
· ·