屋上屋 おくじょうおく
okujōokuo kasu

Godan Verb (su)
Idiomatic Expression

1. to do something useless; to gild the lily; to gild refined gold; to build a roof atop the roof — literal

Related to 屋上架屋
おなじことを なん かい かえすの。屋上 おくじょう すようなくどい説明 せつめい勘弁 かんべんしてよ。
onaji kotō nankai kurikaesuno. okujōyao kasu yōna kudoi setsumēwa kamben shiteyo.
You're wasting your time with all this needless repetition, so spare us the long-winded explanation.