Where does “か行” come from?

か行 (Japanese) comes from Japanese 行, from Middle Chinese 行.

か行 (Japanese): the second row of the 五十音図, consisting of the five kana か/カ, き/キ, く/ク, け/ケ and こ/コ

Definitions

  1. the second row of the 五十音図, consisting of the five kana か/カ, き/キ, く/ク, け/ケ and こ/コ

Ancestry of “か行”, step by step

か行 traces back through two separate lines of ancestry.

via Japanese 行

StepLanguageWordMeaning
1Japanese行a line of text; a row of a matrix; Abbreviation...
2Middle Chinese行—

via Japanese か

StepLanguageWordMeaning
1Japaneseかfinal interrogative particle, similar to a...
2Japaneseいつかsometime, at some point
Every word from Middle Chinese 行 →Every word from Japanese 行 →
か行 — Etymology, Origin & Word History | Etymology Explorer