Where does “夏日” come from?

夏日 (Japanese) comes from Japanese 日, from Old Japanese 日, from Proto-Japonic *pi — day, sun.

夏日 (Japanese): summer day

Definitions

  1. summer day

Ancestry of “夏日”, step by step

夏日 traces back through two separate lines of ancestry.

via Japanese 日

StepLanguageWordMeaning
1Japanese日Sunday
2Old Japanese日the sun; sunlight, sunshine; daytime, daylight
3Proto-Japonic*piday, sun

via Japanese 夏

StepLanguageWordMeaning
1Japanese夏summer; summer according to the lunisolar...
2Middle Chinese夏—
Every word from Proto-Japonic *pi →Every word from Old Japanese 日 →Every word from Japanese 日 →