Why is the ninth month called September?
early 15c., "moderation; intermediate state or amount," from Middle French médiocrité and directly from Latin mediocritatem (nominative mediocritas) "a middle state, middling condition, medium," from mediocris (see mediocre). Neutral at first; disparaging sense began to predominate from late 16c. The meaning "person of mediocre abilities or attainments" is from 1690s. Before the tinge of disparagement crept in, another name for the Golden Mean was golden mediocrity.