idiopathic hypersomnia
A medical term for excessive daytime sleepiness of unknown cause, distinct from narcolepsy or sleep apnea.
Patients with idiopathic hypersomnia feel strong daytime sleepiness even after getting enough sleep.
Compound of 特発性 (idiopathic) + 過眠症 (hypersomnia). The exact historical derivation is uncertain; the term follows standard medical naming conventions.