Green’s Dictionary of Slang

throne n.

also king’s throne, throne room

a lavatory.

J. Churchill ‘Seniority’ in Poems II 131: ‘Let who will go, first, to the Priapan Throne; / A person may do what he will, in his own;’ / And, moving about, he the vapor increas’d; /( things of this kind, there’s some smell and some taste!).
[Ire]Joyce Ulysses 38: In a Greek watercloset he breathed his last...With beaded mitre and with crozier, stalled upon his throne .
[US]Monteleone Criminal Sl. (rev. edn) 238: throne [...] throne room [...] a toilet.
Bakersfield Californian (CA) 6 Feb. 14/7: [advert] At give-away prices: bathroom ‘thrones’ [...] and other plumbing fixtures.
[UK](con. c.1918) D. Holman-Hunt My Grandmothers and I (1987) 55: ‘PLEASE POLISH THRONE’, said a notice pinned to the wall.
[US]G.L. Coon Meanwhile, Back at the Front (1962) 134: She pushed a dung barrow / Singing ‘Dung balls and honey / All fresh from the throne.’.
[US]Times (San Mateo, CA) 5 Oct. 21/1: [advert] Sunken tiled tub and recessed ‘throne’.
[US]Baker et al. CUSS 147: King’s throne Washroom.
[UK]H.E. Bates A Little of What You Fancy (1985) 478: I always use the Throne.
[US]B. Rodgers Queens’ Vernacular 194: public toilet [...] throne room. [Ibid.] 196: throne (camp) toilet seat.
[US]Maledicta IV:2 (Winter) 235: In ordinary slang throne = toilet seat and on the throne = taking a crap.
[US]Star Tribune (Minneapolis, MI) 21 Feb. 13/2: I entered the women’s rest room [...] I ‘ascended the throne’ in the lavatory.
[Ire]D. Healy Bend for Home 262: We’ll be on the throne all fucking night, says Maisie.
[US]Mad mag. Feb. 43: Where in the palace does Jabba go to ease his 30' colon? The ‘throne room,’ of course.
[US]S. King Dreamcatcher 113: Dead and sitting on the throne, just like Elvis.
[UK]Roger’s Profanisaurus in Viz Apr. 47: brownian motion n. [...] painful and frequent visits to the throne room.
[UK]D. O’Donnell Locked Ward (2013) 184: Allie was seated on the throne all right, but he still had his trackie bottoms on.

In phrases

pretender to the throne (n.) (US gay)

1. a heterosexual who poses as gay for the purposes of avoiding the draft.

[US]B. Rodgers Queens’ Vernacular 154: pretender to the throne [...] 2. young man who tries to get out of being drafted by claiming homoerotic tendencies.
[US]Maledicta IV:2 (Winter) 235: A pretender to the throne is someone who falsely confesses to being homosexual [...] to avoid the draft.

2. a vice squad policeman who poses as gay to entrap genuine homosexuals.

[US]B. Rodgers Queens’ Vernacular 154: pretender to the throne 1. vice squad officer.
[US]Maledicta IV:2 (Winter) 235: A pretender to the throne is [...] in another usage, a vice cop who loiters as if he were ‘gay’ to entrap ‘gays’ who might solict public sex, as in a men’s room.
sit on the throne (v.)

to use a lavatory.

[US]Kerouac letter 25 March in Charters II (1999) 360: When I sit on the throne at night I close the light and open the window and look out on the field.
[UK](con. 1930s) J. Wolveridge He Don’t Know ‘A’ from a Bull’s Foot 8: For going to the Lav we used euphemisms like [...] ‘I’m going to have to sit on the Throne.’.
[UK]Barltrop & Wolveridge Muvver Tongue 44: A man says he is going to pay his respects, or ease his mind, or sit on the throne.
[UK]Partridge DSUE (8th edn) 1225/2: [...] since ca. 1920.
[UK]Stage (London) 6 Aug. 10/1: Sitting on the Throne [...] The lack of loos in Bolton is giving bosses [...] a headache. Hundreds of people [...] are ‘caught sahort’.

SE in slang uses

In phrases