mountain often climbed in summer; popular summer hiking mountain
Describes a mountain that is frequently climbed during the summer season, often implying it is a popular destination for summer hikers.
Mt. Fuji is a famous mountain often climbed in summer.
Compound of 夏 (natsu, 'summer') and 山 (yama, 'mountain'). The exact historical derivation is straightforward; the word simply combines the two elements.