Isn't "be on someone" commonly used as someone's responsibility or someone's treat? Is it also used as someone is having something?
Yes, to "be on someone" could mean that it is their responsibility or that they are treating someone. However in this case, to be "on someone" refers to an object literally being on or on top of someone, meaning that they have it. Ex: The bird is on her. Ex: Do you have your wallet on you?
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