text: who invented the term 'blue moon'? can you have two blue moons in a year?   the modern definition is the occurrence of two full moons in a month  is termed as blue moon.the earliest known recorded usage was in 1528, in a pamphlet entitled rede me and be not wrothe: "yf they say the mone is belewe, we must believe that it is true". this implies the expression had a meaning of something that was absurd, and bears close resemblance to another moon-related adage first recorded in the following year "they woulde make men beleue ... that ye moone is made of grene chese".