Green’s Dictionary of Slang

(US) the hand.

[1663		A. Oudin Dictionnaire italien et françois n.p.: la pygne [i.e. peigne, comb] d’Aleman].
1690		Pagan Prince n.p.: Then to comb his head with a German comb, that is to say, his four fingers and thumb.
1784		Rabelais Works (trans Ozell) I 195: [H]e combed his Head with a Comb de Al-main, which is the four Fingers and the Thumb.
1857		T. Wright Dict. Obsolete & Provincial Eng. 505: german comb, s. The fingers, alluding to the slovenliness ascribed to the Germans.
1898		Brewer Dict. Phrase & Fable 512: German Comb. The four fingers and thumb .‘Se pygnoit du pygne d’Almaing’ (Rabelais) .
1979		Maledicta III:2 159: German comb n A hand; from the alleged unsophistication of the Germans who used their fingers to straighten their hair.
1989		H. Rawson Dict. of Invective (1991) 171: Later generations produced such unflattering references as German comb, the fingers.

(US Und.) beer.

1909

F.H. Tillotson How I Became a Detective 88: ‘German delight’ means beer.

see separate entries.

(US) a beer belly, a noticeable paunch.

1927		Lancaster Eagle-Gaz. (OH) 24 June 1/3: [I]t was found that Rev. Roberts had a flask in his pocket and that Mr William Petty had a ‘German Goitre’.
1928		Atchison Dly Globe (KS) 13 Mar. 9/3: Harry Ham’s German goitre has become less noticeable.
1930		Lincoln Jrnl Star (NE) 27 June 20/8: That bay window, German goitre, fallen chest, / Or what you will / Is going to be right heavy, / Thru the ten rounds of the mill.
1941		Geraldine Rev. (MT) 30 July 4/5: The solution for men of forty and over is to control this ‘bay window’ or —‘German goitre’ with a corset.
1952		Great Falls Leader (MT) 23 Aug. 10/2: [A] big beautiful hunk of a man [...] except for a, shall we say, fallen chest or German goitre.
1963		Beaver Cty News (Milford, UT) 8 Aug. 1/1: Father Valine looked at a local suds emporium proprietor and made a remark about his ‘German goitre’.
1971		St Cloud Times (MN) 26 July 20/2: For the man with the big German goitre as it was commonly called in the yesteryear, or a protruding stomach, a special chair was built [...] [the] ‘Belly chair’.
1982		Herald (Jasper, IN) 28 Oct. 9/4: Beer is fattening as is attested to by millions of ‘German goitres’ or bay windows.

vain boasting, megalomania, self-aggrandizement.

1900		Illus. London News 17 Mar. 2/1: When the vivid imagination of a minister of the German gospel turns Tommy Atkins into a black man, my St. Petersburg correspondent need not be astonished at the inveterate prejudice of his Russian friends.
1909		J. Ware Passing Eng. of the Victorian Era 40/1: German gospel (Peoples’, November 1897). Bounce, vain boasting, megalomania. From a phrase addressed in this month by Prince Henry of Prussia to his brother of Germany at a dinner: ‘The gospel that emanates from your Majesty’s sacred person, etc.’.
1914		Lincs. Echo 22 Sept. 2/4: The German Gospel. Dr. Lenard, Professor of Physics, at Heidelberg. has issued a violent pamphlet against England, entitled, ‘England and Germany the Tune of the Groat War’.
1989		H. Rawson Dict. of Invective (1991) 171: Later generations produced such unflattering references as German comb, the fingers, [...] German gospel, boasting.

(orig. gay) the glans penis.

1972		B. Rodgers Queens’ Vernacular.
1986–7		Maledicta IX 56: German helmet n [R] Glans penis; homosexual slang.
2015		I. Welsh Decent Ride 159: Ah’m [...] pittin my boaby intae [the water]. Jist gittin it aw clean under the Jerry helmet.

(gay) amphetamines, esp. Methedrine, a German invention.

1972		B. Rodgers Queens’ Vernacular 95: German marching pills (kwn Texas, late ’60s) amphetamines, especially methedrine.
1986–7		Maledicta IX 56: German marching pills n [R] Amphetamines esp. methedrine; homosexual slang.

(US) to perform oral sex.

1992		Bentley & Corbett Prison Sl. 63: Polish the Old German Helmet Oral sex.
2003		‘Maureen’s Lusty Confessions’ on Apartment 231 🌐 My head is spinning at the mere thought of you hungrily feasting like a famished orphan on my sushi taco. Once you are finished eating my flowers way down south in Dixie, it will be my turn to polish your old German helmet...
2007		T. Dorsey Hurricane Punch 129: That slang’s possibly offensive [...] I’ll use ‘spank the monkey’ or ‘burnishing the German helmet.’.
2013		‘Odd Ball’ in N. Armbrister Complete Poetry 1 n.p.: stroke the devil snail, drink the beer, / polish the German helmet / find Hitler’s missing bollock.