bursa
n.,
pl. 3sae 73sc8 or 3sas 5ModL < ML, a purse, bag: see PURSE6 Anat. a sac or pouchlike cavity, esp. one containing a fluid that reduces friction, as between a tendon and bone
bur4sal
adj.
And, when a bursa becomes inflamed, as the often do, "bursitis" can be very painful.
And in college, the "bursar" was the head of the business office.