Fios:Related to synonymous *blēdū, but with no known Indo-European cognates. Matasović says Pennaod’s connection of this word with Proto-Indo-European *bʰleyd- (“pale”) (compare Old Church Slavonic блѣдъ (blědŭ, “pale”), Old English blāt (“pale”), Lithuanian blaĩvas (“whitish”) “is possible formally…[but] the semantic connection is weak.” Stokes suggests Proto-Indo-European *ǵʰleydʰ- (“to glide”) (Proto-Germanic *glīdaną), but MacBain writes that an evolution of ǵʰ- into Celtic b- is doubtful. --Wikt