From an unattested verb *mikt (“to press, to hit”) (with an extra l), from Proto-Baltic *mik-, from Proto-Indo-European *mei-, *mi- (“to press, to hit”) (whence also Latvian miegt (“to squeeze”)) with an extra k. The semantic evolution was probably “hit, beaten, squeezed” > “made soft by hitting, squeezing” > “made soft (by other reasons, e.g. humidity)” > “humid, damp.” Cognates include Lithuanian mi̇̀klas, miklùs (“agile, nimble, flexible”).