fen·ny \ˈfenē, -ni\adjective Etymology: Middle English, from Old English fennig, from fenn marsh + -ig -y — more at fen 1.: having the characteristics of a fen : boggy < the fenny ground along the lake shore > 2.: peculiar to or found in a fen < long fenny grass > < fillet of a fenny snake, in the caldron boil and bake — Shakespeare >