I remember in the late 60's when "hot" was cool, and "cool" was definitely not hot. In the early 90's, "cool" was hot, and then became cool (in the "what the heck was I thinkin" type of sense) and "hot" became really cool. At one time, if you were hot, you had a fever; if you were cool, you were just really not interested in much of anything. Then cool became frigid, and hot became "totally hot" and everything was just X:
Xtreme dating
Xtrme sports.
Back in the 70's an "X" was an X. You were marked by Society as a divorcee. In the 1890's, "X" marked the spot where treasure could be found on a treasure map, and where someone who couldn't spell signed their name on a legal contract.
Now with an "X" in front of whatever hobby you partake in, you are an agile, "hot", whatever'er, and you are SO COOL! That's hot...
<shrug>
I give up.
"My bad" sounds just as fitting as anything..
CG