sit down, v. — Green’s Dictionary of Slang

sit down v.

1. (Aus.) to settle in a place, to take up a piece of land.

1847		[A. Harris] (con. 1820s) Settlers & Convicts 314: . They told even the stockman's name who used to ‘sit down’ (live) there.
1941		Baker Popular Dict. Aus. Sl.
1975		K. Willey Ghosts of the Big Country 31: He still ‘sits down’ in ‘The Loo’ for several months each year in a galvanised iron house.

2. (US teen) in fig. use, to make a telling, lasting impression, to have a major effect.

1982–2004

G. Sculatti Catalog of Cool 🌐 (to) sit down (verb): To make an impression, to suggest lasting impact. According to Klaflan (1982), a good idea or great music ‘will definitely sit down, kids.’.

3. of criminals, to confer together.

2014

D.B. Flowers Bangs 245: [He] instructed him to get two handguns and meet him at Blinstrum’s Restaurant, where he and Frankie Jr. had planned to sit down.

SE in slang uses

In phrases

sit down like Miss Priss (v.) (also sit down like Miss Queensie) [the names of fig. lazy women]

(W.I.) to sit around while others are working.

1996

Allsopp Dict. Carib. Eng. Usage 509/2: sit down like Miss Priss [...] sit down like Miss Queensie [...] ? cock ten [i.e. ‘to sit with your legs crossed, esp when others are working’.