Think he's referring to Bare-knuckle, or London Prizefighting Rules. But in the early part of the gloved era, there was no manadatory 8 count or neutral corner rule. So you could stand over a downed fighter, wait for him to rise, and then beat him down again (see Jack Dempsey-Jess Willard for an example of this) Hence the high number of Kd's
:nod The most recent one I know of: 2008-09-05 : Zack Mwekassa 185¾ lbs lost to Jozsef Nagy 191¼ lbs by TKO at 1:55 in round 6 of 12 Nagy was knocked down five times. Mwekassa was down once before the referee stopped bout. : http://boxrec.com/media/index.php?title=Fight:1342262
In the modern era I know that Arnold Taylor came back from four kd's to KO Romeo Anaya in the 14th round. (six kd's in total during that fight).
Not sure about the record, but the guy in my avatar used to get knocked down ALL THE TIME!! When he retired the defunct Boxing Today did a huge article, "Danny Little Red Lopez; knock him down, he'll get up and kill ya!"