"paving stone; worn, rounded stone," c.1600, earlier cobblestone, probably a diminutive of cob in some sense. The verb in this sense is from 1690s. Related: Cobbled; cobbling.
"to mend clumsily," late 15c., perhaps a back-formation from cobbler (n.1), or from cob, via a notion of lumps. Related: Cobbled; cobbling.