The story
Blend of ypsilon (“referring to the y-nauplius and y-cyprid larvae”) + kentrogon or vermigon (“similar forms of other crustaceans”).
Etymology from Wiktionary, CC BY-SA 4.0.
ypsigon
Today it means: The amorphous post-larval stage of the crustacean Hansenocaris, a parasite whose host is unknown. Full definition →