Green Tomato and Onion Chow.

Grama's (both family sides) green tomato and onion chow.
Goes by the name "chow chow" all over North America.
Closely related to Picalilly (relish). Unsure where this type of "pickles" comes from.
A close approximation is Habitant Chow Chow Green Tomato.
Habitant is a Smuckers brand.
Howard's Picalilli Green Tomato is reasonably close.

So looking for a recipe?
Chow [Yahoo Answers]
Bernardin Chow
Both of the above involve cabbage and peppers.

But for Canadian variants.
A. Mostly no one grew peppers (wrong climate).
B. Cabbages were relatively hard to grow (pests).

Here is a straightforward formula more in line with the version of my childhood
Elizabeths Chow Chow [Food.com]

Take any of the formulas and go with green tomatos and onions (roughly equal portions - less onions) and make them up to the "other" veggie totals. Omit all other veggies. Use the spices you favor, but the core is made up of mustard and tumeric. Boiling/cooking longer to soften the tomatoes and onions, and evenly embue them with tang/spices, gives a better product by my tastes. Proportions of sugar, salt and vinegar control sweetness and tang. Cornstarch is there to thicken if you wish. Leave it out and cut the water for authenticity, though it might then end up less smooth if not cooked until the tomatoes soften.

Recap of rough ingredients:
Green tomato, onion, sugar, water, vinegar, salt, cornstarch, mustard, turmeric.