from Webster's:

ses·sion Pronunciation: 'se-sh&n Function: noun Etymology: Middle English, from Middle French, from Latin session-, sessio, literally, act of sitting, from sedEre to sit --

Date: 14th century 1 : a meeting or series of meetings of a body (as a court or legislature) for the transaction of business
6 : a meeting or period devoted to a particular activity

So it would look like we just need to find out why it is a "JAM" session......rather then a "music" session or "tune" session...or

MMario