fly-blow, v. — Green’s Dictionary of Slang

fly-blow v.

[SE flyblow, the egg of a fly, which turns into a maggot that will, in this context, figuratively devour the victim’s reputation or money]

1. (US) to gossip maliciously about an absent third party, to attack behind one’s back.

1809		B.H. Malkin (trans.) Adventures of Gil Blas (1822) III 99: The marquis de Marialva had at first taken a fancy to Narcissa [...] when that cockatrice Estella contrived to fly blow the bill of fare, and transfer the banquet to her own untainted charms.
1904		G.D. Chase ‘Cape Cod Dialect’ in DN II:vi 425: fly-blow, v. To slight, to attempt to depreciate.

2. to harass, to pursue.

1874

Leeds Times 28 Mar. 6/5: It was — ’ard as a man couldn’t drop into a ’ouse to ’ave a civil pint with ’is pal but wot he must ’ave a — wench fly-blowin’ about arter ’im.

3. (Aus.) to take money from someone, often by chicanery.

1941

Baker Popular Dict. Aus. Sl.