Mrs. Harris. An hypothetical lady, to whom Sarah Gamp referred
for the corroboration of all her statements, and the bank on which she
might draw to any extent for self-praise. (
“Not Mrs. Harris in the immortal narrative was more quoted and more mythical.” —Lord Lytton.
Harry (To) = to harass. Facetiously said to be derived from Harry VIII. of England, who no doubt played up old Harry with church property. Of course, the real derivation is the Anglo-Saxon herian, to plunder, from hare (2 syl.), an army.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894