The oldest use of “X’s daddy” to refer to someone other than X’s father or father figure dates back to 1681… It was used by prostitutes "in reference to their pimps or to an older male customer. The connection was that pimps - a mostly male group - took care of the prostitutes financially, much like how a father provides for his child’s financial needs.

https://www.acelinguist.com/2017/11/the-deal-with-daddy.html?m=1