The watershed of lake Fragasso is mainly served on the east side by the route 175 which connects the cities of Quebec and Saguenay.

Then, the current from the latter crosses 2.7 kilometres (1.7 mi) to the west of the Lac des Alliés to its mouth.

From 1930, this toponym was replaced by the name "Fossambault Lake" whose justification could not be established; consequently, in 1990, the Commission de toponymie du Québec adopted the old designation, now the only official one.

This toponym evokes the life work of Michel Fragasso (1888-1954), originally from Carignola, in the province of Foggia, in Italy.

[2] The toponym "lac Fragasso" was formalized on October 19, 1990, by the Commission de toponymie du Québec.