late 14c., "periodical sitting of a court," from O.Fr. session,
from L. sessionem
) "act of sitting," from pp. stem of sedere
"to sit" (see sedentary
). Sense of "period set aside for some activity" is first recorded 1920, in bull session,
probably from quarter sessions
courts (see quarter
). Musical sense of "recording occasion in a studio" is from 1927.