Green’s Dictionary of Slang

(UK Und.) a petty thief, who will grab anything, irrespective of its value.

1781		G. Parker View of Society II 54: Fidlum Ben. These are a kind of general tradesmen, who are likewise called Peter’ Sons, with every finger a fish-hook. They watch all opportunities, rob at all times and all places, from a diamond ring on a lady’s toilet down to a dish-clout in the sinkhole.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Fidlam ben, general thieves, also called St. Peter’s sons having every finger a fish hook; (cant).
1811		Lex. Balatronicum.
1834		‘Jack Downing’ Andrew Jackson 92: [He] compelled every mountybank, and elbow-shaker, frezier, bully-trap, and janizary, lolly-poop, sea-crab, caper merchant. Badger, Dandy-pratt, and Fidlam-ben [...] tu muster in his army.
c.1850		Duncombe New and Improved Flash Dict. n.p.: Fidlom Bens [sic] general thieves; called, also, Sons of St. Peter; id est, having every finger a fish-hook.
1859		Matsell Vocabulum 31: fidlam bens. Thieves who have no particular lay, whose every finger is a fish-hook; fellows that will steal any thing they can remove.
1864, 1867, 1870		Hotten Sl. Dict.
1874		Cairo Bull. (Cairo, IL) 5 Nov. 2/3: [from The Graphic, London] Lame Jake, the fidlam-ben, / For shoving spuds, my dears, / Went up the old stone pitcher road.
1881		Trumble Sl. Dict. (1890).