The story
From a Nipmuck (Loup A) word, translated by Ives Goddard as "fishing place at the boundary" or "lake divided by islands". Chaubunagungamaug is the form used by the US government and it occurs in the earliest local records, according to Goddard. In 1921, a local fancifully enlarged the name to Lake Chargoggagoggmanchauggagoggchaubunagungamaugg.
Etymology from Wiktionary, CC BY-SA 4.0.