smell fishy
To seem suspicious of being improper, untoward, or duplicitous. A: "Their numbers don't match up with the taxes they've paid." B: "Hmm, something smells fishy." He thought Janet's response seemed a bit fishy, so he did a bit of investigation into her role in the company.
smell fishy
to seem suspicious. Barlowe squinted a bit. Something smells fishy here, he thought. something about the deal smelled fishy—too good to be true.
smell fishy
Be suspect or suspicious, as in His explanation definitely smells fishy; my guess is that he's lying. This idiom alludes to the fact that fresh fish have no odor but stale or rotten ones do. [Early 1800s]
smell fishy
in. to seem suspicious. (see also fishy.) Marlowe squinted a bit. Something smells fishy here, he thought.
smell fishy, to
To be suspect. This term, which refers to the fact that fresh fish do not smell but stale or rotten ones do, has been around since the early nineteenth century. J. G. Holland explained it explicitly (Everyday Topics, 1876): “Fish is good, but fishy is always bad.” The metaphor turns up in James Payn’s Confidential Agent (1880): “His French is very fishy.”