Etymology
From Middle English titmose, compound of tit (“small bird”) and mose, from Old English māse (“titmouse”), from Proto-West Germanic *maisā, from Proto-Germanic *maisǭ (compare Dutch mees, German Meise, Old Norse meisingr, French mésange), from *maisaz (“tiny, puny”) (compare Norwegian meis (“skinny weakling”)). Spelling as well as the plural form in imitation of the otherwise unrelated mouse.