According to Wikipedia "The name titmouse is attested from the 14th century, composed of the Old English name for the bird, mase (Proto-Germanic *maison, German Meise) and tit, denoting something small. The spelling was influenced by mouse in the 16th century."
I used to think they were called titmice because of the little gray tuft on the top of their head possibly resembling a mouses tit. So much for where my mind goes.
These little birds have been regular visitors to the feeders throughout the winter and will also be around through the summer. They are curious and frequently stop by and peek in the windows as this one is doing. (If you want a fuller stare-down, click on the photo.)