English
mountainous
From mountain + -ous after Middle French montagneux, from Late Latin montāniōsus, from montānia, from Latin montem (“mountain”).
Formed from mountain + -ous
Proto-Indo-European *men- ‘to stand out, tower’
…
Latin mōns ‘mountain, mount’
Early Medieval Latin montānia
Anglo-Norman muntaine
Middle English mountayne ‘a mountain’
English mountain
Today it means
adj Having many mountains; characterized by mountains; of the nature of a mountain; rough (terrain); rocky.
Language periods are conventional ranges, not dates for this word.
Etymograph / mountainous