de- + duct(duc-)

合計からのsubtractionがdeduction

subtract or take away (an amount or part) from a total: 合計から(量や一部を)引いたり取り除くこと

【全体から】〈一定額･一部分など〉を差し引く, 控除する(subtract) «from» (!しばしば受け身で)

e.g. tax has been deducted from the payments. : 支払いから税は差し引かれています。

e.g. Income tax will be deducted from your salary. : 所得税は賃金から差し引かれます.

late Middle English: from Latin deduct- ‘taken or led away’, from the verb deducere. Deduct and deduce were not distinguished in sense until the mid 17th century.