Ganglion cyst: etymology

[bitwise]

Defintion of ganglion from http://dictionary.reference.com/search?q=ganglion:

1. Anatomy. A group of nerve cells forming a nerve center, especially one located outside the brain or spinal cord.
   2. A center of power, activity, or energy.
   3. Pathology. A benign cystic lesion resembling a tumor, occurring in a tendon sheath or joint capsule.

[From Greek, cystlike tumor, nerve bundle.]

A fluid-filled sac protruding from a tendon sheath has little to do with a bunch of nerves, so why are they called the same thing? What is the etymology of “ganglion”? The dictionary wasn’t much help.

[Walloon]

Oxford English Dictionary:

a. Gr. ganglion a tumour under the skin, on or near tendons or sinews; used by Galen to denote the complex nerve-centres, and now chiefly employed in that sense.

[Nametag]

A ganglion is a knot-like bundle, whether of nervous or cystic tissue.