The term donk was originated from the idea of a donk bet (bet into the preflop aggressor) and went on to mean a bad player since that is usually a bad move. It had nothing to do with donkeys or bad play directly until way later. lol

Also, there was a poker player who did a case study that proved that losing players were something like 30x+ more likely to use the word "donk" to describe one of their opponents.

Just be the better person.