Alpine mountain, from German Matte "meadow, pastureland" (see mead (n.2)) + Horn (see horn (n.)). So called for its horn-like shape (cut by glaciers in the Ice Ages). The slopes are steep and treacherous; the Matte is for the meadows at its base. The Roman name was Mons Silvius, which might be based on a personal name.

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Definitions of Matterhorn from WordNet

Matterhorn (n.)
a mountain in the Alps on the border between Switzerland and Italy (14,780 feet high); noted for its distinctive shape;