The M itself doesn't refer to anything. It is simply a signifier for the whole word "musing". There is a new logo icon in the works, so the M you see today in the top left of the website will look different very soon.

If you're wondering what the word "musing" means, by google's definition, it is a period of deep thought. That's why we chose to call this website musing.io - because at the end of the day, what it all boils down to is being able to enjoy the process of thinking and learning and at the same time being rewarded for it.