heartworm

The term 'heartworm' is a transparent Modern English compound, formed by directly combining two native Germanic roots. The first element, 'heart', derives from the Old English heorte, a term with deep Indo-European roots signifying the vital central organ. The second element, 'worm', originates from Old English wyrm, a word with a broad semantic range covering serpents and creeping creatures, which later specialized to mean parasitic helminths. The compound's logic is perfectly literal, describing a parasitic worm that inhabits the host's heart, a meaning that emerged in veterinary medicine to specifically identify the dangerous filarial nematode Dirofilaria immitis.

Structure: heart (organ) + worm (parasite) heart: From Old English heorte, of Germanic origin; related to Dutch hart and German Herz, from an Indo-European root shared by Latin cor, cord- and Greek kēr, kardia. Denotes the central circulatory organ. worm: From Old English wyrm, meaning 'serpent, snake, dragon, insect', of Germanic origin; related to Latin vermis 'worm' and Greek rhomox 'woodworm'. Denotes a creeping or parasitic invertebrate.