long illness that will not heal; chronic lingering illness
Rare term for a prolonged, intractable illness. Not commonly used in modern Japanese; more typical expressions include 長患い or 慢性病.
The word 病閹 can be found in old texts.
The exact derivation is uncertain. The kanji 閹 is rare and typically associated with castration or eunuchs, so its use here may be ateji or a historical borrowing; the compound is not productive in modern Japanese.