Q From Steven Gibbs, Guernsey: The dormouse says in Alice in Wonderland: ‘You know you say things are much of a muchness — did you ever see such a thing as a drawing of a muchness?’ Alice couldn’t explain — can you?
A Muchness is much plus -ness, so the quality of being much. It has been around since medieval times, but in Lewis Carroll’s time it was no more common than it is today. It has never quite vanished from the language, but survives mainly in this set phrase much of a muchness.
Much is a more tricky word than it seems: it often has a sense of “to a great extent; a great deal”; it can also introduce some comparison or relative quantity where the idea of large size is missing, as in adjective phrases like so much, how much, and that much. So you can say things like “The nights were so much longer than the days” or “We can’t push the analogy much further”.
It’s that relative sense that turns up in the saying, where there’s no strong idea of large size, merely of comparison, so that much of a muchness means no more than “very similar” or “just about the same”.