by 1788 as an English word in physiology, shortened from medieval Latin bursa mucosa "mucus pouch," from Medieval Latin bursa "bag, purse," from Late Latin bursa, variant of byrsa "hide," from Greek byrsa "hide, skin, wineskin, drum," of unknown origin; cf. purse (n.).
bursa bur·sa (bûr'sə)
n. pl. bur·sas or bur·sae (-sē)
A sac or saclike bodily cavity, especially one containing a viscous lubricating fluid and located between a tendon and a bone or at points of friction between moving structures.