Subtrahend
... is the same in English and German.
subtrahend means: in a subtraction problem the subtrahend is what you take away. In 12-3 you take away 3. The 3 is therefore the subtrahend. The number you start with is the minuend. The result is called difference:
12 - 3 = 9
minuend: 12
subtrahend: 3
difference: 9