From an unattested verb *balt (“to become white”) (of which balts originally was the past participle form; compare Lithuanian bálti, and Latvian 17th-century derived verb baltīt (“to make, paint something white”), later replaced by other verbs, derived from balts: from Proto-Baltic *bal-, from Proto-Indo-European *bʰel-, *bʰol- (“shiny, white”). Cognates include Lithuanian báltas, Sudovian bałtas. In several Indo-European languages, reflexes of the stem *bʰel-, *bʰol- are often found in words relating to water or humid places, probably due to their shiny, reflective surfaces: Illyrian *balta (“marsh, swamp”), Albanian baltë (“mud, sludge, swamp”), Proto-Slavic *bolto (“swamp, lake”) (Old Church Slavonic блато (blato, “lake”), Russian болото (boloto, “marsh, swamp”) (dialectal “puddle, lake”), Czech bláto (“mud; pl. swamp”), Polish błoto (“mud, swamp”)). This usage is also attested in Baltic languages, as in, e.g., Old Prussian placename Namuynbalt (swamp). It left also traces in Latvian, in the names of lakes or swamps (Baltenis, Baltiņa purvs), and is a possible source of the word balti (“Balts, Baltic”).