E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Hal.
A familiar contraction of Harry (for Henry). Similarly, Dol is a contraction of Dorothy; Mol, of Mary, etc.
1
The substitution of P for M as the initial letter of proper names is seen in such examples as Polly for Molly, Patty for Martha, Peggy for Margy (i.e. Margaret), etc. (See ELIZABETH.)