perineurium
noun
peri·neu·ri·um ˌper-ə-ˈnu̇r-ē-əm 
-ˈnyu̇r-
plural perineuria ˌper-ə-ˈnu̇r-ē-ə
-ˈnyu̇r-
: the connective-tissue sheath that surrounds a bundle of nerve fibers
Word History
Etymology
New Latin, from peri- + Greek neuron nerve — more at nerve
First Known Use
1867, in the meaning defined above
Medical Definition
perineurium
noun
peri·neu·ri·um ˌper-ə-ˈn(y)u̇r-ē-əm
plural perineuria -ē-ə
: the sheath of connective tissue that surrounds a bundle of nerve fibers