source: How to Add and Subtract Rational Numbers

sub-(下に) + tract(引く)

verb with object

take away (a number or amount) from another to calculate the difference: 差を計算するために別のものから(数字や量を)差し引くこと

«…から» 〈数･量など〉を引く, 減じる; 差し引く, 控除する(deduct) «from» (↔ add)

subtract 43 from 60. : 60から43を引く

take away (something) from something else so as to decrease the size, number, or amount: 大きさ、数字、量が減るように他の何かから(何かを)引く

programs were added and subtracted as called for. : プログラムは必要に応じて追加されたり差し引かれたりした

mid 16th century: from Latin subtract- ‘drawn away’, from sub- ‘from below’ + trahere ‘to draw’.