A short nap. Forty is an indefinite number, meaning a few. Thus, we say, “A, B, C, and forty more.” Coriolanus says, “I could beat forty of them” (iii. 1). (See Forty.)
“The slave had forty thousand lives.”
I loved Ophelia; forty thousand brothers Could not, with all their quantity of love, Make up my sum.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894