Google it and you’ll get an instant answer but the roots are Eminem’s song Stan.
Dictionary
stan
INFORMAL
noun
noun: stan; plural noun: stans
an overzealous or obsessive fan of a particular celebrity.
"he has millions of stans who are obsessed with him and call him a rap god"
verb
verb: stan; 3rd person present: stans; past tense: stanned; past participle: stanned; gerund or present participle: stanning
be an overzealous or obsessive fan of a particular celebrity.
"y'all know I stan for Katy Perry, so I was excited to see the artwork for her upcoming album"
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