weld: [16] Weld is ultimately the same verb as well (as in ‘The tears welled up in his eyes’). This originally meant ‘boil, melt’, but in the 15th century (perhaps under the influence of Swedish välla ‘gush, weld’) it began to be used for ‘fuse metal by heating’. Weld itself presumably arose from the use of the past form welled as a present form. => well[weld etymology, weld origin, 英语词源]