I recently had a large, squishy lump at the point of my elbow, and the doctor told me my bursa had filled with fluid. This sounded so much like bursar that I wondered if the two were related. And it turns out that they are.

bursa – a sac between muscles, tendons, or skin, and bony prominences, to lessen friction
[Latin bursa bag, purse, from Greek βνρσα hide, wine-skin]
bursar – a treasurer, esp. of a college [from bursa. The concept of a ‘bag of money’?]

It looks like purser and purse are related too. OED is not certain how the initial b- of bursar changed to a p-, but it notes that the same b-to-p shift occurred to change the old bodin ‘sausage’ into today’s word pudding.