出典:Wiktionary
From Middle English seldscene, seltsene (“まれに encountered, seldom seen; まれに; as adv. seldom, まれに”), from 古期英語 seldsīne, seldsēne (“まれに, extraordinary, unfamiliar, まれに”). Cognate with Old High German seltsāni, Modern German seltsam.
seldseen (not comparable)