I suspect the clue is in your phrasing: Latinization. European scholars wrote in Latin, where "k" is uncommon and "kl" almost unknown, and transliterated Εὐκλεί

I suspect the clue is in your phrasing: Latinization. European scholars wrote in Latin, where "k" is uncommon and "kl" almost unknown, and transliterated Εὐκλείδης as "Euclidis". Later writers in French and English - but probably not in Germanic languages other than English - turned this into "Euclid". If the Elements was discovered now, we'd probably favour a more direct transliteration of the Greek: Eukleidos.