As Wikipedia says, the etymology of the name "karbovanets" is debatable: by one supposition it originated in Ukraine from the ancient primitive way to carve (karbuvaty, Ukrainian: Кapбyвaти) numbers of calculations on a rod, and by another supposition – from the carving (incision) on a rim of a metal coin rouble.
I like first opinion, because ukrainian word KARB means notch, groove, carved or superseded by special tool on the surface of something; nick, scar. So we carve karbs here on a long stick, not mine blocks on a blockchain to mark transactuins and for doing this we receive karbowanec (karbovanets - english transliteration)