na-adjective
meaningful; suggestive; seeming to have a story
Archaic adjectival noun describing someone or something that appears to have a hidden past, deep meaning, or circumstances that are hard to explain. Rare in modern Japanese; mostly encountered in older literature.
彼の微笑みは由ありげで、何か秘密があるように見えた。
His smile was suggestive, as if he had some secret.
その古い屋敷は由ありげな雰囲気を漂わせていた。
The old mansion had an atmosphere that seemed to be with a history.
Modern and common; means 'meaningful' or 'suggestive' in a straightforward way, without the archaic or literary nuance of 由ありげ.
Similar meaning but more common in modern usage; implies there is a story or complicated circumstances behind something.
Compound of 由 (よし, 'reason', 'history') + あり (exist) + げ (suffix indicating appearance or seeming). The exact historical derivation is uncertain, but the word follows a classical pattern for forming adjectival nouns.