sityoudaoicibaDictYouDict[sit 词源字典]
sit: [OE] Sit comes from a prehistoric Germanic *sitjan or *setjan, which also produced German sitzen, Dutch zitten, Swedish sitta, and Danish sidde. This was derived from a base *set-, source also of English seat, set (etymologically ‘cause to sit’), and settle. And this in turn went back to the Indo-European base *sed- ‘sit’, which has contributed hugely to English vocabulary – mainly through its Latin descendant sedēre ‘sit’ (source of English assess, insidious, séance, session, size, subsidy, etc), but also via Welsh, in the form of eisteddfod.

It lies in addition behind English saddle and soot, and its other progeny include Russian sidet’, Serbo-Croat sjediti, and Latvian sēdēt ‘sit’.
=> assess, eisteddfod, insidious, saddle, séance, seat, session, set, settle, size, subsidy[sit etymology, sit origin, 英语词源]
sit (v.)youdaoicibaDictYouDict
Old English sittan "to occupy a seat, be seated, sit down, seat oneself; remain, continue; settle, encamp, occupy; lie in wait; besiege" (class V strong verb; past tense sæt, past participle seten), from Proto-Germanic *setjan (cognates: Old Saxon sittian, Old Norse sitja, Danish sidde, Old Frisian sitta, Middle Dutch sitten, Dutch zitten, Old High German sizzan, German sitzen, Gothic sitan), from PIE root *sed- (1) "to sit" (see sedentary).

With past tense sat, formerly also set, now restricted to dialect, and sate, now archaic; and past participle sat, formerly sitten. In reference to a legislative assembly, from 1510s. Meaning "to baby-sit" is recorded from 1966.

To sit back "be inactive" is from 1943. To sit on one's hands was originally "to withhold applause" (1926); later, "to do nothing" (1959). To sit around "be idle, do nothing" is 1915, American English. To sit out "not take part" is from 1650s. Sitting pretty is from 1916.