An Etymological Dictionary of the German Language/Lügner
Lügner, m., ‘liar,’ from MidHG. lügenœre, OHG. luginâri. To this common Teut. root lug (Aryan lugh), ‘to lie,’ Goth. liugan (pret. liugaida), ‘to marry,’ has no relation; the latter, like OFris. logia, ‘to marry,’ is connected rather with OIr. luige, ‘oath’ (primit. form lughio-). ModHG. lügen is more probably allied to OSlov. lŭžą (lŭgati), ‘to lie,’ lŭža, ‘lie.’ From Teut., Ital. (dial.) luchina, ‘false story,’ is derived.