fuse, fut=注ぐ、融ける

confuse / 共に注ぐ→注ぎあって区別がつかない→混同する、混乱する

cf. The new rules have caused a lot of confusion.

profuse / 前に注ぐ→ばらまくほどある→豊富な

cf. I've never seen flowers in such profusion.

futile / 注ぐことができる→ごぼれやすい→無駄な、無益な

cf. Our efforts to revive the dog were futile.