Shit, shower, and shave (the British military called it "[ablutions]") was a phrase that originated in [WWI], where the US military tried to "train" soldiers to perform certain functions ( to shit, shower, and you guessed it) in the morning so as to not be interrupted during actual combat (WWI was primarily a "[daylight]" war). By the end of [WWII], combat was a 24 hour event, and they could never actually TRAIN the body to crap [on command], so the practice was dropped. I've never heard anyone use it who wasn't a veteran of WWII. My dad (a WWII marine) used to say it in the morning and assumed that I (A Vietnam vet) knew what he was talking about. I just thought to myself "gee, dad, that's a weird thing to share..."