From Proto-Italic *luksos, from Proto-Indo-European *lug-so-s, from Proto-Indo-European *lewg- (“bend, twist”), whence also luctor (“wrestle”). Cognate with Sanskrit रुग्ण (rugṇá, “bent, broken”), Ancient Greek λύγος (lúgos, “twig, withe”), Lithuanian lugnas, Old Norse lykna (“to bend, close”).
Practice speaking and memorizing "luxus" and many other words and sentences in Latin.