At least three rationales have been suggested for the origin of the name Pyrex. Reflecting its initial use for cookware, including pie pans, it could be either an English–Latin (py = pie + rex = king) hybrid for “pie king” or a Greek–Latin hybrid (pyr = fire + rex) for “fire king”, or a contraction for its most important physical property: low thermal (pyr) expansion (ex) (6). As it turns out, none of these are correct, though the first version is closer to the truth than the others. Reflecting its use for glass pie pans, it was originally called “Pie Rite” or “Py-Right”, but the name was eventually changed to Pyrex in order to rhyme with “Nonex”, an earlier brand of borosilicate glass marketed by Corning for use in railroad signal lamps (7).

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