How young are you? The word “scant” does not belong exclusively to the world of cooking; it is a real word, used, we thought, in fairly normal conversation.
According to the dictionary, scant means, “1. inadequate in size or amount; not enough; meager. 2. lacking a small part of the whole; not quite up to full measure. 3. to furnish with an inadequate supply, short ration, etc.”
So in the cooking world, you’re looking for the second part of the second definition – not quite up to full measure. You great-grandmother was asking you to add not quite 2 tablespoons of yeast. So instead of heaping tablespoons, or leveled-off tablespoons, you want slightly undernourished tablespoons.
She could have said 1-7/8 Tbsp, or 1-3/4 Tbsp, but that wasn’t exactly your great-grandmother’s style, was it? She wanted to improve your vocabulary while helping you cook.
The word comes, as you probably already guessed, from the Old Norse scammr, which means “short.”