æfter + mæþ

Aftermath comes from Old English æfter ('after') + mæþ ('a mowing, a crop of grass'), from the verb māwan ('to mow'). The mæþ was not the grass itself but the act of cutting it — and by extension the crop produced by that cutting. The aftermath was, literally, the second mowing: the new growth of grass that appeared in a field after the first harvest had been taken. It was an agricultural term of precise technical meaning, describing a specific phase in the management of meadowland. Farmers who owned the aftermath rights to a field could graze their cattle on the regrowth or take a second, lesser hay crop.