E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Spitting for Luck.
Boys often spit on a piece of money given to them for luck. Boxers spit upon their hands for luck Fishwomen not unfrequently spit upon their hansel (i.e. the first money they take) for luck. Spitting was a charm against fascination among the ancient Greeks and Romans. Pliny says it averted witchcraft, and availed in giving to an enemy a shrewder blow.