Ignis Fatuus, Jack-o'-Lantern, Morass: Origins, Forms, Histories of Words Meaning Marsh, Swamp

The natural features of a region are its topography (Greek topos, "place"). Marshes, swamps, and related areas are important examples of topographic features.

In the current alphabetic series of terms that refer to such places, here are the origins, forms, and histories of ignis fatuus, jack-o'-lantern, and morass. The dates of forms and meanings come from the Oxford English Dictionary and Merriam-Webster's Collegiate Dictionary.

Ignis Fatuus
The term ignis fatuus (plural, ignes fatui) entered English in the 16th century from Medieval Latin, where the words mean literally "foolish fire."

The phrase ignis fatuus refers to a light that sometimes appears in the night over marshy ground and usually occurs as a result of the combustion of gas from decomposed organic matter (c. 1563).

Typically such a light flashes and disappears quickly. A series of such lights in the same vicinity presents the impression that one light is suddenly moving, vanishing, and reappearing elsewhere.

That impression is the source of the folk belief that an ignis fatuus is the work of a mischievous marsh spirit deliberately leading travelers astray, sometimes into dangerous ground. From that belief comes a figurative meaning of ignis fatuus: a deceptive or elusive goal or hope (1599).

An ignis fatuus, in both its concrete and its figurative senses, is popularly called a jack-o'-lantern and a will-o'-the-wisp.

Jack-o'-Lantern
Jack-o'-lantern, or jack-a-lantern, entered English in the 17th century in the form Jack-with-the-lantern (1663), literally meaning a man with a lantern (portable lamp) and usually referring specifically to a night watchman. That use of the expression is obsolete.

However, English speakers soon made an association between the night light of the watchman and the night light of the marshy ignis fatuus (see ignis fatuus above). Since at least 1673, jack-o'-lantern, or any one of its early forms (such as Jack with a lanthorn and Jack-a-lantern), has been used synonymously for ignis fatuus in both its concrete and its figurative senses.

Morass
Morass entered English in the 17th century from Dutch moeras, a modification of Old French maresc, of Germanic origin. The word is akin to Old English mersc ("marsh").

Morass denotes specifically a marsh or a swamp, or, more generally, any boggy land (1655).

Figuratively, anything that traps, confuses, or impedes is a morass (1867)
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Encyclopaedia Britannica Ready Reference 2004. CD-ROM. Encyclopaedia Britannica, 2004.

Merriam-Webster's Collegiate Dictionary. 11th ed. Springfield, Mass.: Merriam-Webster, 2006.

Merriam-Webster's Geographical Dictionary. 3rd ed. Springfield, Mass.: Merriam-Webster, 2007.

The Oxford English Dictionary. 2nd ed. Oxford, England: Clarendon Press, 1989.