Meaning may have evolved from “stalk, reed pipe” to “shinbone”, the latter being used by Pliny and later authors; flutes were originally made from shinbones. Possibly connected to Ancient Greek σίφων (síphōn, “siphon, tube”), the irregular forms suggesting a non-Indo-European loan or substrate source, but as if from pseudo- or regional Proto-Indo-European *tweybʰ-. There are no solid IE cognates outside of the Greek word, though comparisons to Proto-Slavic *stьbъ (“stalk”) have been drawn. Compare tuba (“trumpet”), tubus (“tube”), possibly from the same substrate source.