At the root of murder is an interesting phoneme, which I believe comes from the Greek. It is related to myrmidons, myrmex, the French Merde, myriad… and the implication is a flowing thing whose beginning or end is difficult to identify. Myrmex is a term used in relation to ants. And of course, a ‘murder’ of crows… follows this theme… it is a flowing, without beginning or end (although in modern times crow groups often tend to be smaller). An actual murder, of course, often has a (copious) flow of blood associated with it. Similarly, with the term murmur… and the word murmuration… which describes the endless flowing shapes that starlings may make when flying in their unique ‘changing cloud’ groups.