The word 'shirokujichu' (meaning all the time) is derived from the four times of the day known as 'shiji' (early morning, noon, late afternoon and dusk) in combination with the six times of the day known as 'rokuji.'
「四六時中」の語源は、四時（早晨・午時・晡時・黄昏）と六時をあわせたもの。