The literal translation of mea culpa that I've always seen is "through my fault." (Three years of latin sticks with you even after thirty years.) Susan, by works for me instead of through, although I don't see where the word "own" comes from. ESquared's version is completely interpretive, grammatically dissimilar to the latin phrase. As Susan states, it is used in prayer: often, a more complete excerpt is mea culpa, mea culpa, mea maxima culpa, which works out to "through my fault, through my fault, through my most grievous fault." This makes the "I am to blame" version even more cumbersome to backform.
I think people try to use it today literally as the slang, "my bad." (Which is grammatically incorrect, but nowadays most people can't even spell, much less parse grammar.)
And if you think etymology and translation lack the nature of a puzzle or challenge, boy, are you wrong!
Getting back to the original question, anybody else hear George Carlin's riff on "kit and caboodle?" It's along the lines of: if you have the whole kit, why do you need a caboodle? Can you get the caboodle without the kit? -- Ah, well, it's much funnier when Carlin tells it.