Elinvar is a nickel-iron alloy notable for having a modulus of elasticity which does not change much with temperature changes. The name is a contraction of the French elasticité invariable (elastically invariable). It was invented by Charles Édouard Guillaume, a Swiss physicist who also invented Invar, another alloy of nickel and iron with very low thermal expansion. Guillaume won the 1920 Nobel Prize in Physics for these discoveries, which shows how important these alloys were for scientific instruments. - Source: Wikipedia