"Zat fish," Cloiseau said, "is not a suspect, but 'e definitely knows somezing about zis case. We should interrogate 'im. 'E is a poisson of interest."
Professor Higgs was certain now. This sub-atomic particle was not the one they were searching for, but he needed to question it carefully. It was definitely a boson of interest.
That clergyman wasn't the one who buggered the choirboys. But he does know the bishop, so we should question him. He's a parson of interest.
Those fried-&-dried snacks from western India aren't the culprits. But bring them to the interrogation room. They are farsans of interest.