The physical lake was formed during the Ice Age as a direct result of melting glaciers, and this was approximately 10,000 years ago. After archaeological studying, scientists found that the land was used upto 7,000 years before Christ, possibly as a water source and stopover site. By the time modern land ownership came around, there were two main land owners; these two being Charles Dyer (owning the northside) and John Snell (owning the southside). This is where Heart Lake's first two names came from, Dyer Lake or Snell's Lake. In 1913, the lake was noted by many for its pristine water quality, until the 1920s when a duck, plant, and feces infestation took place. The final owner before TRCA was Colonel AE Taylor, who spread the theory that the lake was occupied by a Loch-Ness Monster type serpent who could spit water fifteen feet high. To protect from any further damage to the physical lake and it's reputation, the TRCA took control of the land in 1956, making the land a conservation area for anyone to enjoy. Please look at this article for more.
Heart Lake is heart shaped. Although it was formerly named after its landowner, John Snell (Snell's Lake).