You have to go to the vulgar dictionaries of the 18th-early 19th c. to find many of these cant words. The OED (through the 1987 Supplements) still omits many of the entries in these compendia, probably to spare our sensibilities. Flash house (house of prostitution), flash cove or flash covess (sometimes abbess- the master or mistress of a flash ken), flash man (the bully: pimp, and bouncer) have all been admitted to the OED, (p. 289 of the letter F in the 1971 edition, I don't know the edition you consulted).
Look for this in addition to the one I cited:
"The Scoundrels Dictionary: or, an Explanation of the Cant Words used by Thieves, House-breakers, Street Robbers, and Pickpockets about Town. To Which are prefixed Some Curious Dissertations on the Art of Wheedling, and a Collection of their Flash Songs, with a Proper Glossary..." Second Ed., London, 1788. It has been reprinted, I understand. The one I quote (1811) is copied from this edition.

Curious- What were the Irish "fragments"? I don't believe that they have been quoted in Mudcat. ???
The first edition, 1785, was written by Capt. Francis Grose, a British antiquarian because he ran short of funds.
More digression: These works define "pig" as a policeman, and "bread" as money, both still in current use.
Among those not entered into the OED (and I don't blame the compilers) are terms such as dingleberry- little balls of excrement hanging around the anus. I am glad that we don't have to suffer the odors of those days.