The name "Cacaoui" is a variant of kakawi, the local name of the long-tailed duck. According to Placide Vigneau, who wrote about the Mingan Archipelago and Havre-Saint-Pierre, the duck's name should be written as kakawit, and the local people of the Havre-Saint-Pierre region pronounce it as cacaoite. The duck is loquacious, with a musical call that sounds like "ah-ah-wè", which may be the basis for the name. The name was approved by the Geography Commission in 1945.
Dam
IOC, a Rio Tinto subsidiary, owns the SM-2 hydroelectric plant on the Sainte-Marguerite River. IOC also owned the wooden dam on the Cacaoui Lake reservoir. This dam was built in 1950. It had fallen into decay and was dismantled in 2010 and replaced with a structure of local rocks to naturally control the water flowing into the western part of the lake. The work was done by the Groupe Nordique, and involved dismantling several buildings and dams, and recovering iron. The rockfill weir is high and long. The reservoir has an area of. The watershed covers.
Environment
The lake is in the boreal climate zone. A map of the Ecological regions of Quebec places the lake in the 6J-S ecological subregion, part of the eastern spruce/moss domain of the boreal zone. The average annual temperature in the neighborhood is. The warmest month is July, when the average temperature is, and the coldest is January, with. The region is one of mountains that rise high above their surroundings, with rocky escarpments. The network of lakes and rivers is enclosed in narrow valleys. The Forêt ancienne du Lac-Cacaoui, an exceptional forest ecosystem occupies part of the southern shore of the lake. The forest contains small islands of a few hectares of Picea glauca up to high within stands of Picea mariana. The spruce is dominated by Abies balsamea, which is well adapted to the cold and damp climate. The area of old-growth forest was designated IUCN Management Category III at a national level in 2008. It is managed by the Ministère des Forêts, de la Faune et des Parcs.
Visiting
The lake is within the Matimekzone d'exploitation contrôlée. The Zec rents a cabin to visitors that can sleep four people. The cabin has a wood stove, propane fridge and cooker, and solar electricity supplying the lighting system. In September 2018 two brothers died in a boating accident on the lake. This part of the lake is over deep in places, and divers were unable to find the bodies.
