What is the origin of the idiom "conflict of interest" and when to use it?

The idiom 'conflict of interest' originated in the mid-20th century and is used in situations where individuals or entities have dual roles or interests that could potentially make it hard for them to be fair. It is often used in legal, ethical, and professional contexts where transparency, fairness, and honesty are crucial. It is a reminder to be careful when people have different interests that could get in the way of doing the right thing.