Green’s Dictionary of Slang

1. a fool, a stupid person; thus attrib.

1614		Jonson Bartholomew Fair III i: Let’s enquire of Master Leatherhead.
c.1698		B.E. Dict. Canting Crew n.p.: Leather-head a Thick-skull’d Heavy-headed Fellow.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1842		Whip & Satirist of NY & Brooklyn (NY) 23 July n.p.: the whip wants to know [...] If a certain class of leathers heads [...] had no more wit than to get drunk and make such fools of themselves .
1845		D. Corcoran Pickings from N.O. Picayune (1847) 22: You be d---d, old leather head.
1864		J. Horrocks letter in My Dear Parents 17 Sept. 97: As for filling Coal pits in Wigan, that’s a job for leatherheads.
1869		Cairo Eve. Bull. (IL) 28 June 1/3: A Leatherhead, who is a leatherhead, in truth.
1876		Manchester Courier 10 Apr. 3/2: What a stupid old leather-head you must be.
1884		P. Woolley Trottings of a Tenderfoot n.p.: Now the Senator is only a leatherhead who made his pile by such and such a swindle [F&H].
1896		G.F. Northall Warwickshire Word-Book 133: Leatherhead. A numskull, dolt.
1897		Roanoke Times (VA) 12 Nov. 2/3: I had a chum that a great big leather-head boy that was always [...] accidentally making trouble.
1906		Dly Public Ledger (Maysville, KY) 18 Sept. 1/1: A big rock was thrown by a bigger leatherhead into the ‘sand hopper’.
1910		Sporting Times 1 Jan. 1/4: ‘Can you tell me what town this is, guv’nor?’ ‘Oh, Leatherhead.’ ‘Who are yer callin’ names?’.
1911		S.F. Call 9 Aug. 6/6: You called me leatherhead and chump.
1928		M. Meredith ‘The Human Head in Sl.’ in AS III:5 409: Other expressions which one sometimes hears or sees in popular speech [...] ‘leatherhead,’ ‘tin can,’ ‘dome,’ or ‘solid ivory’ (dome).
1997		Share Slanguage.

2. (US) an inhabitant of Pennsylvania.

1845		St Louis (MO) Reveille 14 May 2/4: The inhabitants of [...] Pennsylvania [are called] Leatherheads [DA].
1866		Amer. Citizen (Butler, PA) 26 Sept. 2/4: Nicknames [...] Pennsylvania, leather heads.
1872		Harper’s Mag. Jan. 318/1: Below will be found a careful compilation of the various nicknames given to the States and people of this republic: [...] Pennsylvania, Pennites, and Leatherheads [DA].
1886		Chicago Weekly News 29 Apr. 4/3: Pennsylvania is the Keystone state from its position in the middle of the arch of the original thirteen states, but its people are Leatherheads for some unknown reason [DA].
1894		Cape Girardeau Democrat (MO) 3 Nov. 5/4: He had placed them in the salesroom for stamping [...] and not for the purpose of offering to sell them [...] as this Leatherhead vagbond would have the people believe.
1903		Commoner (Lincoln, NE) 12 Nov. 13/2: Newcomers from pennsylvania are called Leatherheads.
1909		J. Ware Passing Eng. of the Victorian Era 194/1: Leatherheads (American). People of Pennsylvania – probably from their early puritanic origin – still very marked.

3. (US) a policeman or watchman [the protective leather helmets worn by the police, or the leather badges that New York’s first policemen wore].

1846		D. Corcoran Picking from the Picayune 22: A Dutch [i.e. German] watchman came up, who looked like a mammoth locomotive head of cabbage [...] ‘You be d—d, old leather head,’ said O’Toole.
1846		N.O. Delta 2 Sept. 2/4: Watchman. — He said as how I was a leather-sconced corporate reality, and that we leatherheads were the only real offering of chartered rights [DA].
1868		M.H. Smith Sunshine and Shadow in N.Y. 148: The guardians of the city were watchmen [...] and were known as leather-heads, from the leather cap they wore [DA].
1869		Cairo Eve. Bull. (IL) 28 June 1/3: A Leatherhead, whi is a leatherhead, in truth.
1887		(ref. to 1835) G. Davis Recoll. Sea-Wanderer 174: The fire-bells were rung, the prison officials were bewildered, and the 'leather-heads' (as the city police or night watchmen were then called) assisted in quenching the fire and preserving order.
1888		N.Y. Mercury 21 July n.p.: Here the old police or leatherheads tried to restrain them, but in vain [F&H].
1890		(ref. to early–mid-19C) G.W. Walling Recollections 32: During the first half of the present century the police were known as ‘Leatherheads,’ a nickname which arose from the fact that they wore leather hats, something like an old-fashioned fireman’s helmet, with a broad brim behind.
1927		(ref. to 1890s) H.C. Brown In the Golden Nineties 177: The ‘leatherheads’ (now ‘cops’) used to make periodical descents on them.
1930		(con. 1820s–40s) H. Asbury Ye Olde Fire Laddies 101: These hats were made of leather [...] They gave the early New York Policeman his sobriquet of Leatherhead.
1947		M. Crane Sins of N.Y. 11: The town called these watchmen ‘leatherheads’ because of the heavy helmets they wore on duty, not unlike those that adorn a fireman in action today [DA].

4. (US) a louse [their seeming indestructibility].

1926

N. Klein ‘Hobo Lingo’ in AS I:12 652: Leather-heads — certain lice.