c.1380 as singular, replaced by early 17c. by mathematics (1581), from L. mathematica (pl.), from Gk. mathematike tekhne "mathematical science," fem. sing. of mathematikos (adj.) "relating to mathematics, scientific," from mathema (gen. mathematos) "science, knowledge, mathematical knowledge," related to manthanein "to learn," from PIE base *mn-/*men-/*mon- "to think, have one's mind aroused" (cf. Gk. menthere "to care," Lith. mandras "wide-awake," O.C.S. madru "wise, sage," Goth. mundonsis "to look at," Ger. munter "awake, lively"). Mathematics (pl.) originally denoted the mathematical sciences collectively, including geometry, astronomy, optics. Math is the Amer.Eng. shortening, attested from 1890; the British preference, maths is attested from 1911.

I bet you didn't know it came from a PIE base, but pie are square.