Where does “いつか” come from?

いつか (Old Japanese) comes from Old Japanese いつ, from Proto-Japonic etu — five.

いつか (Old Japanese): sometime, at some point

Definitions

  1. sometime, at some point

Ancestry of “いつか”, step by step

いつか traces back through two separate lines of ancestry.

via Old Japanese いつ

StepLanguageWordMeaning
1Old Japaneseいつ—
2Proto-Japonicetufive

via Old Japanese か

StepLanguageWordMeaning
1Old Japaneseか—
Every word from Proto-Japonic etu →Every word from Old Japanese いつ →