The phrase "God Damnit", which when expressed in a grammatically correct fashion would read "God Damn It," is a vulgarity used to express frustration. It's literal definition is "May the Christian God Damn it to Hell". In slang, it is a phrase used in a generally non-religious context. For example, if one cannot get an electronic device to work properly, one might exclaim "God Damnit!", meaning that you are so upset with the device you wish that God would condemn it to eternal damnation.

It is rarely used literally, and is considered a lesser of vulgarities, though to the extremely religious it is considered highly offensive. In the Christian faith it is considered a violation of one of the ten commandments.

I couldn’t care less (but one must keep up appearances, right?)

last word of every sentence. usually adds authority.

The politically correct term to describe the feeling of life grabbing you by the balls.

Life sucks!

an expression beavers use when their dam breaks

Why would God create something, and then damn it?

Goddamnit originated from spain where it ment something like, "horsecock" or "damned be thy son". Noone knows how, or why, it has been common in the English language.

From it's originated state, it has become somewhat false in the English language, where many still belive it's just "God Damn It!" without spaces. God himself knows this is wrong.

Today it means something (1.) important, and/or (2.) something worth making a statement over. It can also mean that you are (3.) embarrased over something.