The story
From Dease + lake. Coined by Scottish-born Canadian John McLeod in 1834, regional Chief Trader of the Hudson's Bay Company. Named after Canadian explorer and fur trader Peter Warren Dease (1778–1863), a Hudson's Bay Company factor. The town is located on the southern end of the lake, and named for it. The Indian reserve is located in the area of the lake and named for it.
Etymology from Wiktionary, CC BY-SA 4.0.