Etymology

Either from Swedish brun or Middle Low German brūn. Cognate to Norwegian brun, Danish brun, Low German bruun, Dutch bruin, English brown, German braun. Ultimately derived from Proto-Germanic *brūnaz, from Proto-Indo-European *bʰruHn-, enlargement of *bʰrew- ‎(“shiny, brown”)

Further Indo-European cognates: Lithuanian bė́ras ‎(“brown”), Sanskrit बभ्रु ‎(babhru, “reddish-brown”)