From Proto-Balto-Slavic *daugjas, from Proto-Indo-European *dʰowgʰ-, the o-grade form of *dʰewgʰ- (“to affect, to press; to produce”), from the stem *dʰew-, a variant of *tew- (“to swell”). The meaning changed from “to swell, swollen” to “big” and then “a lot, much”. Note that the river name Daugava contains the same stem (originally “large river, with much water”). Cognates include Lithuanian daũg, Sudovian daug, Proto-Slavic *dužь (Russian дю́жий (djúžij, “heavy, strong, healthy”), dialectal ду́жий (dúžij), Belarusian ду́жа (dúža, “a lot”), ду́жы (dúžy, “strong”), Ukrainian ду́жий (dúžyj), ду́же (dúže, “very, a lot”), Czech duži (“strong”), Polish duży (“big, grown up”), dużo (“much, many, a lot”)), Gothic 𐌳𐌰𐌿𐌲 (daug, “is useful”), Old High German tugan, German taugen (“to be useful”), Sanskrit दोग्धि (dógdhi) (< *dʰowgʰ-) “to milk” (< “to press”), Ancient Greek τεύχειν (teúkhein, “to prepare, to create”).