九日
ここのか · kokonoka · JLPT N5 · noun
days
📅 九日 = nine + day; kokono (native nine) + ka (day counter)
Days 2-10 of the month use old native Japanese numbers plus -ka. Nine is kokonotsu, so drop -tsu and add -ka: kokono-ka. Same pattern as mikka (3rd) and nanoka (7th). It means both the 9th and a span of nine days.
九 — single stroke; bent hook form
九 originally pictured a bent arm or elbow, drawn as a curved hooked line. It was borrowed phonetically to write the number 'nine' because the words sounded alike, and that numeric meaning eventually replaced the original.
日 — pictograph of the sun
日 is a pictograph of the sun, originally drawn as a circle with a dot or stroke inside representing the sun's substance. Over time the round shape was squared off into the modern rectangular form. It means 'sun' and by extension 'day'.