From Proto-Baltic *walg-, from the o-grade form of Proto-Indo-European *welg- (“humid”), from the stem *wel- (“to press, to squeeze”) with an extra g (a parallel form *welk- with k gave rise to Latvian valkans (“wet and soft”)). The semantic change was probably from “pressed, squeezed (so as to become soft)” > “soft (also from other reasons, e.g. humidity)” > “humid.” Other ablaut forms gave rise to dialectal synonymous forms like velgs and vilgs, as well as the standard term vilgt (“to become moist, humid”). Cognates include Lithuanian vi̇̀lgti (“to become wet”), vi̇̀lgyti, Proto-Slavic *volga (“humidity, moisture”) (Old Church Slavonic влага (vlaga), Russian влага (vlaga), Bulgarian влага (vlaga), Belarusian вільгаць (vilʹhacʹ), Ukrainian волога (voloha), Czech vláha), Old High German wëlk (“humid, soft”), German welk (“faded”), Old High German wolkan, German Wolke (“cloud”), Thracian olgan(o) (“humid”).