An Orillian lung maggot was an undesirable creature.

In 2373, facing imminent death in a plasma explosion, Neelix told Tosin that he would have no problem dying if it would get rid of an Orillian lung maggot like him. (VOY: "Fair Trade")

Presumably this is a larva (a juvenile form that metamorphoses into an adult) of a creature hailing from or discovered by "Orill".
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