Late 16th century; earliest use found in Philip Sidney (1554–1586), author and courtier. From mountain + -ette, after Middle French montaignete from montagne + -ette.
Definition of mountainette in US English:
mountainette
nounˌmaʊntɪˈnɛt
A small mountain; a hillock, mound.
Origin
Late 16th century; earliest use found in Philip Sidney (1554–1586), author and courtier. From mountain + -ette, after Middle French montaignete from montagne + -ette.