: any of a class or order (Oligochaeta) of hermaphroditic terrestrial or aquatic annelids (such as an earthworm) that lack a specialized head
from the stem of New Latin Oligochaeta, class name, from oligo-oligo- + -chaeta "having hair or bristles (of the kind specified)," neuter plural noun derivative based on Greek -chaitēs, adjective derivative of chaítē "hair, flowing locks, mane of a horse" — more at chaeta
The taxon Oligochaeta was introduced by the German zoologist Adolph Eduard Grube (1812-80) in "Die Familien der Annelida," Archiv für Naturgeschichte, 16. Jahrgang (1850), 1. Band, p. 275. The name refers to the fact that most animals in the order lack parapodia and have few or no bristles (chaetae) in comparison to polychaetes. Compare polychaete.