MIDDLE OF THE RUGGED MOUNTAIN

Something mediocre is pretty middle-of-the-road, but etymologically speaking it's more like middle-of-the-mountain. Borrowed in the 1580s from a Middle French word with the same spelling and definition, mediocre derives from the Latin word  mediocris, which meant "ordinary" or "moderate" but had a literal meaning of "halfway up the mountain", because something mediocre is neither at the peak nor at the base of a figurative incline. That's a portmanteau of medius, meaning "middle", and ocris, or "mountain". Medius, through Proto-Italic methios, comes from Proto-Indo-European medhyos, "between". Ocris, meanwhile, traced from PIE hokris, meaning "top", possibly by way of Greek. The graph of usage in literature over time for the word mediocre is pretty situationally ironic: after a peak in 1928, it's decreased and settled about halfway between zero percent and the maximum utilization.