Origin and history of math

1520s, originally "a second crop of grass grown on the same land after the first had been harvested," from after + -math, which is from Old English mæð "a mowing, cutting of grass" (from PIE root *me- (4) "to cut down grass or grain").

Other words for it were aftercrop (1560s), aftergrass (1680s), lattermath, fog (n.2). The figurative sense is by 1650s. Compare French regain "aftermath," from re- + Old French gain, gaain "grass which grows in mown meadows," from Frankish or some other Germanic source similar to Old High German weida "grass, pasture."

When the summer fields are mown,

When the birds are fledged and flown,

     And the dry leaves strew the path;

With the falling of the snow,

With the cawing of the crow,

Once again the fields we mow

     And gather in the aftermath.

[Longfellow, from "Aftermath"]

"the science of quantity; the abstract science which investigates the concepts of numerical and spatial relations," 1580s; see mathematic (the older form of the word in English, attested from late 14c.) + -ics. Originally one of three branches of Aristotelian theoretical science, along with first philosophy (or metaphysics) and physics (or natural philosophy).

Mystical doctrines as to the relation of time to eternity are also reinforced by pure mathematics, for mathematical objects, such as numbers, if real at all, are eternal and not in time. Such eternal objects can be conceived as God's thoughts. [Bertrand Russell, "A History of Western Philosophy"]