The oldtime strongmen lifted just about any weight they could get their hands on. Shown here is a block weight, an obvious precursor to the kettlebell. Block weights (also sometimes referred to as scale weights) were originally used for measurement purposes though eventually many strongmen began to lift them for strength and show.

I suspect that many of the oldtime strongmen noticed these weights sitting backstage at the theaters where they performed (where they were used as ballast to counterweight theatre props etc) and decided to start using them to lift. Block weights are awkward to lift, making movements such as cleans and presses a much bigger challenge, even at comparatively “light” weights. Block weights also make excellent “handles” for pushups and handstands.