In a manner resembling or characterized by grass; with an abundance of grass.
Formed from 'grass' (Old English 'gærs') through the adjectival suffix '-y' plus the adverbial suffix '-ly' (Old English 'lice'). Standard English adverb formation.
The '-ly' suffix comes from an Old English word meaning 'like' or 'resembling'—every time you add '-ly' to an adjective, you're literally saying 'in a [adjective]-like manner,' a pattern that's held for over a thousand years.
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