how does an expression become an expression? do you just have to say it enough until it catches on? "well, you know, god isn't always naked", "deaf dogs don't bite", "a mime in a jar isn't always a hemophiliac". it clearly doesn't have to make any sense. does it have to be recognized by some governing body? do you just have to be able to say, "it's an expression" after you say it. "a slice off a cut loaf is never missed" is an expression referring to having sex with someone who isn't a virgin. it makes zero sense. it's an expression, but like a lot of expressions, it's completely wrong. who doesn't miss a slice of bread? you get down to your last sandwich and have uneven slices. furious. the weirdest expression i've ever heard, which i didn't believe was an expression until i heard it from several people who didn't know each other is, "he wouldn't piss on me if i were on fire in the middle of the desert." well, whoever he is sounds like a gentleman. why would you want him to pee on you? "oh god! i'm on fire! if only someone would have have the decency to expell all the urine from their bladder upon my person!" why not hope for water? or that they would pour their drink on you? (but why would they have a drink in the desert?) or maybe that they would be kind enough to let you die in peace. pee wouldn't extinguish anything, and the whole act would probably just confuse the hell out of you. "i'm laying their in flames. screaming. out of nowhere, this dude shows up and pees all over me ...and then just walks away. by the time i rolled around and got the flames out, what little skin i had left had the unmistakable aroma of burnt urine mixed in with it. if i ever see that guy again, i'm going to jam my melted nub right into his ass!" - which should be an expression.