1680s, "tumor, swelling;" 1732 as "bundle of nerves," from Greek ganglion "tumor under the skin," used by Galen for "nerve bundle;" of unknown origin. According to Galen, the proper sense of the word was "anything gathered into a ball."
1680s, in anatomy, "an interlacing of nerves, vessels, or fibers," Modern Latin, literally "braid, network," noun use of past participle of Latin plectere "to twine, braid, fold," from suffixed form of PIE root *plek- "to plait." Original use in solar plexus "network of nerves in the abdomen" (see solar). General sense of "net-like arrangement of parts" is from 1760s. Related: Plexal.
<a href="https://www.etymonline.com/word/ganglia">Etymology of ganglia by etymonline</a>
Harper, D. (n.d.). Etymology of ganglia. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/ganglia