Deuteronomy 3:9

The Sidonaee call Hermon the fruit-producing Mount, but the Amoraee call it the Snowy Mountain, because the snow never ceases from it either in summer or winter.

HERMON, THE SIDONIANS CALL SIRION, [AND THE AMORITES CALL IT SENIR]. “But in another place Scripture states, even unto Mount Sion which is Hermon. Thus you see that the mountain has four names [Hermon, Sirion, Senir and Sion. Scripture’s reference to this multiplicity of names is] to tell the praise of the Land of Israel because there were four kingdoms priding themselves in this; this one saying ‘After me shall it be called,’ and another saying, ‘After me shall it be called.’” This is Rashi’s language from the words of Agadah.
It is indeed possible that this praise [that four nations were vying for this mountain] is correct but the main purport of the verse is to state that the Sidonians, children of Canaan’s firstborn, called Mount Hermon “Sirion” when it was formerly in their possession; and the Amorites, who now dwelled there and from whom Israel was to capture it, called it “Senir.” [Senir] is a Canaanite word for “snow,” as Rashi testified about it, and as Onkelos also rendered it, [“mountain of snow”]. And because it is a mountain of snow, also on account of its frigid temperature causing it to be bleak [and unapproachable], it is called Hermon [from the word cherem — “banned”], this being a surname of the mountain. Perhaps the name “Sirion” in the Sidonian language indicates this characteristic while the real name of the mountain [as mentioned by the Torah further on] is Sion. The verse stating, from the top of Senir and Hermon [which would seem to indicate that these were two separate mountains], really refers to two surnames of the [same] mountain and thus means “from the top of the snow and the bleakness,” or it may mean “from the top of Senir and from the whole mountain.” Similarly, that which is stated in the Book of Chronicles, And the children of the half-tribe of Menasheh dwelt in the land, from Bashan unto Baal-hermon and Senir and Mount Hermon where they increased also means “and Senir and the whole mountain which is Mount Hermon.” Baal-hermon, however, was a city or a tower which they called “Baal,” or perhaps it was the name of one of the Baal-idols that was worshipped there.
It is possible that after Israel was in the Land, names of places were somewhat changed; this mountain was large — and they called the highest part of its summit Senir, and the second part thereof they called Hermon. Or they may be other mountains which people after the [period of the] Torah called by these names [Senir, Hermon — and they really represent two separate mountains, but the names mentioned in the Torah indicate different names of but one mountain, as explained above]. There are many cases like this. So also, and the Hermons from the hill Mizar [would indicate that there were other mountains by the name of Hermon, for otherwise we have no explanation why they called “the Hermons,” in the plural].