the.com/roundworm

means A parasitic worm with a smooth, unsegmented, cylindrical body — the group includes everything from harmless soil dwellers to the intestinal parasites that have plagued animals and people for as long as we've been keeping records.

from Pure plain English: 'round,' describing the worm's cross-section (unlike flatworms, which are flattened), plus 'worm,' from Old English 'wyrm,' an ancient word for serpent or creeping thing that goes back to a common Germanic root shared with 'worm' across related languages. No hidden story here — the name is a literal, practical description, coined by people who looked at the thing and called it exactly what they saw.