Bursa comes straight from the medieval Latin bursa (purse or bag) which in turn is directly from the Greek bursa (wineskin). As wineskins were produced from animal hides, bursa can ultimately trace its ancestry to the Greek word for ox, bovis, which also gives us "bovine".

During Roman times, bursa was used only as a proper name.

True to its Latin origins, a bursar is one who handles the "purse".

Bursa was first used in its anatomical sense by Bernhard Siegfried Albinus (Weiss) in 1734, who coined the term "mucous bursae" for the lubricating sacs at joints. "Mucous" was dropped with the subsequent characterization of synovial fluid.

A painting on an ancient Greek vase: a Satyros is depicted holding a rhyton (drinking horn) and bursa (wineskin). From the collection of the Boston Museum of Fine arts. Image at www.theoi.com/Gallery/T60.11.html