It originated from the practice of aiming a firearm at a target. The "bead" refers to the small, metal bead that is placed on the top of the barrel of a rifle or shotgun, which helps the shooter aim.
So, if someone says they "have a bead on him", it means they are watching him closely, perhaps with a sense of hostility or suspicion.
Here are some examples of how the phrase might be used:
* "The detective has a bead on the suspect, and he's sure he'll catch him." (Meaning the detective is watching the suspect closely and is confident in apprehending him.)
* "The sniper had a bead on the target, waiting for the perfect moment to fire." (Meaning the sniper was aiming at the target and prepared to shoot.)
* "The boss has a bead on John for the promotion, but he's not sure if John will be able to handle the pressure." (Meaning the boss is observing John and considering him for a promotion.)
It's important to note that this phrase can sometimes have a negative connotation, suggesting that someone is being watched or targeted.