An Etymological Dictionary of Astronomy and Astrophysics

To take one number away from another; deduct. To perform the arithmetic operation of → subtraction.

Etymology (EN): From L. subtractus, p.p. of subtrahere “to draw from beneath, take away, draw off,” from → sub- “from under” + trahere “to pull, draw.”

Etymology (PE): Zirkaršidan, literally “to draw beneath,” from zir-, → sub-, + karšidan “to draw, pul, drag,” variant of kašidan “to draw, protract, trail, drag, carry;”
Av. karš- “to draw; to plow,” karša- “furrow;” Proto-Iranian *kerš-/*xrah- “to draw, plow;” cf. Skt. kars-, kársati “to pull, drag, plow;”
Gk. pelo, pelomai “to move, to bustle;” PIE base k^wels- “to plow.”
Kâhidan, → decrease.