An idiomatic expression used by the people of Six Nations Territory as well as other Iroquois/Haudenosaunee Territories. There is no mainstream English comparison. This term is used as a response to many things, such as a semi-funny joke, somebody doing or saying something stupid, seeing something funny happen (ie. someone falling). This is a very common expression in Six Nations Territory, one cannot go a day without hearing the expression used while visiting the territory.
-Hey I seen your mom at Tim Horton's eatin all the donuts!
-Hahaha, heck init!! Who taught you how to walk?? haha.