～ずつ
～ずつ · ～zutsu · JLPT N5 · noun
time
🍪 zutsu = zu + tsu: two beats, dealt out one share at a time
ずつ follows a number or amount: 一つずつ = one at a time, 少しずつ = little by little, 二人ずつ = two people each. It is thought to come from the old counter つ doubled (つつ), a repeat that signals the same amount again and again.