Said by Roman writers to be of Gaulish origin, from Proto-Celtic *lougā. The Celtic origin is uncertain, since the diphthong -eu- is secondary and the word lacks clear Insular Celtic cognates. There is a possible connection with Proto-Brythonic *llex (“stone”). Simon argues that the Celtic is a borrowing from Germanic, based on reconstructed Proto-West Germanic *leuwa and Gothic *𐌻𐌹𐌲𐌲𐍅𐌰 (*liggwa); however, these forms are unattested, purely conjectural, and are themselves not given any further etymological origin, which weakens the argument considerably.