Sitting
Old English sittan, of Germanic origin; related to Dutch zitten, German sitzen, from an Indo-European root shared by Latin sedere and Greek hezesthai .
wiktionary
From Middle English sittyng, sittynge, equivalent to sit + -ing. Cognate with Dutch zitting(“a sitting, session”), German Sitzung(“a sitting, session”), Swedish sittning(“a sitting, session”).
From Middle English sittinge, sittynge, variant of sittinde, sittende, sittande, from Old English sittende(“sitting”), from Proto-Germanic *sitjandz(“sitting”), present participle of Proto-Germanic *sitjaną(“to sit”), equivalent to sit + -ing. Cognate with West Frisian sittend(“sitting”), Dutch zittend(“sitting”), German sitzend(“sitting”), Swedish sittande(“sitting”), Icelandic sitjandi(“sitting”).
etymonline
sitting (n.)
early 13c., verbal noun from sit (v.). Meaning "a meeting of a body" is from c. 1400. Meaning "interval during which one sits" (for some purpose, especially to have one's portrait taken) is from 1706. Sitting-room first recorded 1771. Slang sitting duck "easy target" first recorded 1944; literal sense is from 1867 (it is considered not sporting to shoot at one).