With all due respect to Funk51:
Ancient Greek and Roman fresco's had pictures of their athletes holding DB shaped weights (stone, no doubt..or crude mental) when long jumping and running. Their soldiers also trained with DB like equipment. Also longer handle weighted bars to get strength in the arms.
Wonder when shot loaded BB's & Db's were first used. Or even the revolving Olympic bar? Men use to train with lighter cannon balls, back in the middle ages. Probably the kettle bell developed from that, just mold a handle on a cannon ball, I guess..