It appears that “tumgluttons” is a colloquial expression from the east coast of Canada, probably from Newfoundland and Labrador where these were found. The term is used to identify mittens designed and used for two purposes, hunting and lobster fishing. The shape of “tumgluttons” appears to be a hybrid of a mitten and a glove (“gluttons”). Each has three sections: one for the thumb (“tum”); the second for the trigger finger, sometimes called a “trigger mitten” used for hunting, the third section holds the other three fingers together for warmth and protection from the elements.
In a popular Newfoundland and Labrador magazine, Downhome, the “thumb glutton mitt” is described as being ”knit using two strands of wool and patterned like a mitt but with glove-like fingers for the trigger finger and thumb.” A single finger was used to pull the trigger of the gun without having to remove the mittens.
For lobster fishing the fingers of the glove/mitten are divided into pairs, resembling a lobster claw. The fingers together keep each other warm. The thumbs get their own pocket, so a jacket can be easily zipped or boots buckled without removing the hands. Bicycle riders highly recommend “lobster mittens” for winter riding. Wearing them, a bicycler can reach the brake without taking the rest of the hand off the handle.