See quotations.
1775. By swamps then in general is to be understood any low grounds subject to inundations, distinguished from marshes, in having a large growth of timber, and much underwood, canes, reeds, wythes, vines, briars and such like, so matted together, that they are in a great measure impenetrable to man or beast.—B. Romans, ‘Florida,’ p. 25.
1821. I agree that swamp mud or, as the Scotch and English farmers call it, peat moss, is not manure; but good manure may be made of swamp mud.—Mass. Spy, Feb. 21: from the Rhode-Island American.
