The word grade is short for “gradient” and the idiom derives from railroad construction in nineteenth-century America. Back in the non-high-tech age of the nineteenth century, calculations had to be carefully made to ensure engines didn’t encounter sudden steep gradients and this is how we ended up with “make the grade.” It appears for the first time in recorded history in 1438 in The Book of Margery Kempe, even though many scholars believe that the idiom in Kempe’s book isn’t entirely clear and probably has a different meaning from its modern use. Back in ancient Rome people didn’t have toilet paper so they had to use a sponge on a stick every time they had to clean themselves after going number two. However, if someone wasn’t being careful when using the stick, they could pick it up by the wrong end and I’m sure you don’t need any more details beyond this point, right? Ewwwww. However, ships owned by pirates would often sail under fake flags from various countries to approach their prey and eventually would show their true colors by hoisting their real flags (aka a pirate flag) once they had conquered the other ship. The strange thing about this phrase is that despite being amazingly popular (millions of people in many different languages use it daily) it doesn’t have a confirmed origin but is believed to be associated with medicine, particularly with the detoxification of drug addicts in rehab.
