Green’s Dictionary of Slang

(US) don’t get yourself over-excited.

1965

C. Himes Cotton Comes to Harlem (1967) 136: Don’t get your breeches torn [...] All you got against me is suspicion of homicide.

to soil one’s trousers through a sudden attack of terror.

1641

R. Brome Jovial Crew IV ii: To the blinde Virgin of fourscore, / And the lame Batchelor, of more, [...] How Venus caus’d their Sport to be / Prepar’d with butter’d Egs.

1. to remain where one is, esp. in a social context; thus to outstay one’s welcome.

1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: sitting breeches, One who stays late in company, is said to have his sitting breeches on, or that he will sit longer than a hen.
1811		Lex. Balatronicum.
1826		‘Geoffrey Grin’ Rhyming Reminiscences 130: And when he had his sitting breeches on, He wouldn't budge an inch.
1856		T. Gwynne Young Singleton 159: Don’t let me turn you out though, as you seem to have your sitting breeches on.
1864		(con. 1837) G. Ticknor Life of William Hickling Prescott 131: , I am very sorry to be obliged to tear myself from you at so very unreasonable an hour ; but you seem to have got your sitting-breeches on for the night.
1908		O. Onions Pedlar’s Pack 141: It’s a bit late—nigh ten by Orion and the Follower yonder—but I’ve my sitting-breeches on if you have.

2. to hold a position.

1837

Coventry Standard 6 Oct. 4/5: The meeting views with the greatest delight the election of Baron Bruit and sincerely hopes that he may long continue to wear his sitting breeches’.

see wear the trousers under trouser n.