The word jungle comes from a Sanskrit term meaning rough and arid
Jungle began life in ancient India as a word for dry, rough ground, not dripping forest. Its tangled, impassable meaning grew partly from a misunderstanding: European explorers travelled by river, saw walls of vegetation on the banks, and assumed the whole forest was just as thick. Much of it was not.
The Sanskrit root jaṅgala meant rough and arid. It reached English in the 18th century through the Hindustani word jaṅgal, meaning forest, and was spelled half a dozen ways along the route. Across the Indian subcontinent and the Iranian Plateau the word still often describes the scrubby growth that replaces old forest or reclaims abandoned land. An Anglo-Indian reading may be what gave it the sense of a dense, tangled thicket.
In its stricter sense, jungle means ground-level vegetation so thick that travellers must hack a path through it. That actually sets it apart from mature rainforest, whose shaded understorey is often fairly open and easy to walk. True jungle springs up where light reaches the floor: after hurricanes or logging open the canopy, along stream banks, and at forest edges. Monsoon forests, with their lianas and shrubs, and mangroves, with prop roots and low canopies, fit the description well.
The river-bank illusion produced a second, looser meaning: almost any humid tropical forest. Before the 1970s, jungle made up over 80 percent of the terms used for such forests in print. Since then, rainforest, a word missing from English dictionaries until that decade, has steadily displaced it, reflecting a shift toward seeing these places as fragile rather than menacing.
The metaphor carries darker baggage: lawlessness, threat, disorientation. Upton Sinclair used The Jungle as the title of his 1906 exposé of exploited Chicago stockyard workers. The phrase law of the jungle comes from Kipling's The Jungle Book of 1894, where, ironically, it names an elaborate code of rules rather than chaos. Post-colonial critics such as Edward Said and Chinua Achebe have examined how Western stories cast the jungle as savage territory to be mastered or feared. The word even lives on in the red junglefowl, the Asian bird domesticated at least five thousand years ago as the main ancestor of the chicken.
Source: Jungle