From Latin 'solidare' (to make solid)—to solder is to solidify a metal joint, sharing its root with soldier.
A fusible metal alloy used to join metallic surfaces, applied in a molten state.
From Old French 'soudure,' from 'souder' (to solder, to consolidate), from Latin 'solidare' (to make solid), from 'solidus' (solid, whole). To solder is etymologically to 'make solid'—to solidify a joint. The 'l' was reinserted from Latin in the 16th century but remains silent in standard pronunciation. Key roots