card, punch card, calorie
卡 centers on a flat, rigid piece of material used for recording or measuring: a card, a punch card, or a calorie (as a unit measured or counted).
卡 is a modern character, likely created as a simplified or borrowed form for 'card'. Its origin is not clearly tied to ancient Chinese character development, and the exact historical derivation is uncertain.
The top 上 looks like a card being held up, and the bottom 卜 looks like a punch or a mark on the card. Together, 卡 is a card that gets punched or marked to record something like calories.
For サ, imagine a card being swiped through a machine with a sharp 'sa' sound: sa -> サ, like the sound of a quick card swipe.
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