Brewer's: A B C Book
A primer, a book in which articles are set in alphabetical order, as the A B C Railway Guide. The old Primers contained the Catechism, as is evident from the lines:
That is question now; And then comes answer like an Absey book.
: King John, i, 1. Shakespeare
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894