late 14c., "periodical sitting of a court," from Old French session "act or state of sitting; assembly," from Latin sessionem (nominative sessio) "act of sitting; a seat; loitering; a session," noun of action from past participle stem of sedere "to sit" (from PIE root *sed- (1) "to sit"). Sense of "period set aside for some activity" is first recorded 1920, in bull session, probably from quarter sessions courts (see quarter (n.1)). Musical sense of "recording occasion in a studio" is from 1927.
"to roost, to alight or settle on or as on a perch; to occupy some elevated position," late 14c., from Old French perchier "to sit on a perch" (of a bird), from perche (n.); see perch (n.1). Related: Perched; perching.