In South Florida we take the word for granted, but what is the meaning of Everglades?

The first known use of the term Everglades is on Turner's map of Florida (1823) and is cited in the Dictionary of American English currently being published by the University of Chicago Press. A map of Florida compiled by an English geographer for the British government and dated 1821 does not show the Everglades. The word seems to have come into use in Florida only after acquisition by the United States in 1819. The Spanish seem to have had no equivalent of 'Everglades'.

An early spelling was 'glad' and it meant bright, shining. 'Glade' in a sense now obsolete except in poetry meant 'a clear place in the sky, a bright streak or patch of light.' Derived from Anglo-Saxon and Icelandic languages, used by peoples in lands where bright waters were seen at some seasons of the year and snow and ice at another, glade was associated with water in any of its several forms... the Merriams' Webster's New International Dictionary defines Everglades (singular) as: 'A swamp or low tract of land inundated with water and interspersed with hummocks or small islands and patches of high grass; chiefly used as 'the Everglades', a great tract of this nature in Florida.

Excerpt from Marjory Stoneman Douglas' Everglades and First Reclamation Idea, an unpublished, undated manuscript at the University of Miami.