What is the X in X-mas?
1590s, "any high, snow-capped mountain," from Alps, from French Alpes, from Latin Alpes "the Alps," perhaps from altus "high," or albus "white" or from a Celtic word (according to Servius), or a pre-Indo-European root. Alps, the European mountain range, attested by that name in English from 1550s.
Mountain system of south-central Europe.
Note: The Alps provide scenic beauty and the location for an abundance of winter sports, making them a popular tourist destination.