by 1970, of unknown origin; perhaps arbitrary (cf. cloud nine). Among the guesses that have been made without real evidence: concrete mixer trucks were said to have dispensed in this amount. Or the yard may be in the slang sense of "one hundred dollars."
Several similar phrases meaning "everything" arose in the 1940s (whole ball of wax, which is likewise of obscure origin, whole schmear); older examples include whole hog (see hog (n.)) and whole shooting match (1896); whole shebang (1895).