連日
れんじつ · renjitsu · JLPT N1 · noun
day
📅 連 (row of) + 日 (day) = a row of days, so every day in a row
連 means to link or run in a series, and 日 is day. Together they describe days strung one after another, which gives the sense of every day.
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'.