尾おひれをつける

お

ひ

れ

を

つ

け

る

Meanings

1

expression, ichidan verb

exaggerate; embellish a story

idiomatic expression

Literally 'to attach a tail fin'; used when someone adds made-up details to a story or rumor, making it more interesting or dramatic than the truth.

を

つけ

て

話はな

す

の

は

やめ

て

ください

。

Please stop spreading rumors with added exaggerations.

尾おひれをつける
Common mixed kanji-kana spelling; 尾ひれ is the most frequent written form for this idiom.
尾お鰭ひれを付つける
Full kanji spelling using 鰭 for ひれ; less common but still seen.
尾おひれを付つける
Variant with を instead of つ; both are used.

誇こ張ちょうする
誇張する is a more formal, direct verb for 'exaggerate', while 尾ひれをつける is an idiomatic expression specifically for adding fictitious details to a narrative.
話はなしを盛もる
話を盛る is a casual slang expression meaning 'to exaggerate a story', similar in meaning but more informal than 尾ひれをつける.

The idiom originates from the image of attaching an extra tail fin to a fish, symbolizing the addition of something unnecessary or false to a story.