aftergrass is a compound of after + grass, denoting the second growth of grass after mowing; after is from Old English æfter ('later') and grass from Old English græs ('grass'), from Proto-Germanic *grasą. Morphologically, the word is transparent as a compound: its parts remain visible in the modern spelling, while the older history of those parts supplies the deeper ancestry. In modern use, the noun sense is "grass that grows after the first crop of hay is cut", which keeps the etymology connected to the word's present dictionary value rather than treating it as a merely historical label. The wider word family includes related English forms such as aftermath, grass, showing how the same base continues to support neighboring English vocabulary. The principal historical forms in the chain include Old English æfter, Old English græs, which anchor the explanation in named linguistic material.