From Kook Science
Achi is a wild man figure that originated with the Tamanacs of the Cuchivero River, near the lower Orinoco, in what is now Venezuela. It was described as a "hairy man of the woods" and an "anthropomorphous monkey" by Alexander von Humboldt in his Personal Narrative of Travels to the Equinoctial Regions of America, who added that was it was likewise known as salvaje (from the Spanish, "savage" or "wild") or as vasitri ("great devil") by the Maipure of the Upper Orinoco River, and that it reputedly "carries off women, constructs huts, and sometimes eats human flesh".
- von Humboldt, Alexander (1907), "The Wild Man of the Woods", in Ross, Thomasina, Personal Narrative of Travels to the Equinoctial Regions of America, During the Year 1799-1804, 2, London: George Bell & Sons, p. 270-272, https://archive.org/details/personalnarrativ02humbuoft/page/270
It was among the cataracts that we began to hear of the hairy man of the woods, called salvaje, that carries off women, constructs huts, and sometimes eats human flesh. The Tamanacs call it achi, and the Maypures vasitri, or 'great devil.' The natives and the missionaries have no doubt of the existence of this man-shaped monkey, of which they entertain a singular dread. Father Gili gravely relates the history of a lady in the town of San Carlos, in the Llanos of Venezuela, who much praised the gentle character and attentions of the man of the woods. She is stated to have lived several years with one in great domestic harmony, and only requested some hunters to take her back, because she and her children (a little hairy also) were weary of living far from the church and the sacraments. The same author, notwithstanding his credulity, acknowledges that he never knew an Indian who asserted positively that he had seen the salvaje with his own eyes. This wild legend, which the missionaries, the European planters, and the negroes of Africa, have no doubt embellished with many features taken from the description of the manners of the orang-otang,[*] the gibbon, the jocko or chimpanzee, and the pongo, followed us, during five years, from the northern to the southern hemisphere. We were everywhere blamed, in the most cultivated class of society, for being the only persons to doubt the existence of the great anthropomorphous monkey of America. There are certain regions where this belief is particularly prevalent among the people; such are the banks of the Upper Orinoco, the valley of Upar near the lake of Maracaybo, the mountains of Santa Martha and of Merida, the provinces of Quixos, and the banks of the Amazon near Tomependa. In all these places, so distant one from the other, it is asserted that the salvaje is easily recognized by the traces of its feet, the toes of which are turned backward. But if there exist a monkey of a large size in the New Continent, how has it happened that for three centuries no man worthy of belief has been able to procure the skin of one? Several hypotheses present themselves to the mind, in order to explain the source of so ancient an error or belief. Has the famous capuchin monkey of Esmeralda (Simia chiropotes), with its long canine teeth, and physiognomy much more like man's[*] than that of the orang-otang, given rise to the fable of the salvaje? It is not so large indeed as the coaita (Simia paniscus); but when seen at the top of a tree, and the head only visible, it might easily be taken for a human being. It may be also (and this opinion appears to me the most probable) that the man of the woods was one of those large bears, the footsteps of which resemble those of a man, and which are believed in every country to attack women. The animal killed in my time at the foot of the mountains of Merida, and sent, by the name of salvaje, to Colonel Ungaro, the governor of the province of Varinas, was in fact a bear with black and smooth fur. Our fellow-traveller, Don Nicolas Soto, had examined it closely. Did the strange idea of a plantigrade animal, the toes of which are placed as if it walked backward, take its origin from the habit of the real savages of the woods, the Indians of the weakest and most timid tribes, of deceiving their enemies, when they enter a forest, or cross a sandy shore, by covering the traces of their feet with sand, or walking backward?
Though I have expressed my doubts of the existence of an unknown species of large monkey in a continent which appears entirely destitute of quadrumanous animals of the family of the orangs, cynocephali, mandrils, and pongos; yet it should be remembered that almost all matters of popular belief, even those most absurd in appearance, rest on real facts, but facts ill observed. In treating them with disdain, the traces of a discovery may often be lost, in natural philosophy as well as in zoology. We will not then admit, with a Spanish author, that the fable of the man of the woods was invented by the artifice of Indian women, who pretended to have been carried off, when they had been long absent unknown to their husbands. Travellers who may hereafter visit the missions of the Orinoco will do well to follow up our researches on the salvaje or great devil of the woods; and examine whether it be some unknown species of bear, or some very rare monkey analogous to the Simia chiropotes, or Simia satanas, which may have given rise to such singular tales.
(* Simia satyrus. We must not believe, notwithstanding the assertions of almost all zoological writers, that the word orang-otang is applied exclusively in the Malay language to the Simia satyrus of Borneo. This expression, on the contrary, means any very large monkey, that resembles man in figure. Marsden's History of Sumatra 3rd edition page 117. Modern zoologists have arbitrarily appropriated provincial names to certain species; and by continuing to prefer these names, strangely disfigured in their orthography, to the Latin systematic names, the confusion of the nomenclature has been increased.)
(* The whole of the features—the expression of the physiognomy; but not the forehead.)