Antifa refers to a loose affiliation of left-wing activists that rose to prominence in the United States in 2017. The idea of "defunding" the police--which is being used to refer variously to reforming, restructuring or reallocating police funding to other needs, or even abolishing the police outright--dates to well before then.
Books and publications advocating for a radical shift in the law enforcement and penal systems began to circulate years before the Antifa movement, spurred by leading activists like Angela Davis. Critical Resistance, for instance, an organization that advocates for police and prison abolition, was founded in 1997.