In English we know Aegithalos caudatus as the long-tailed tit. It’s a tit-type passerine bird with a long tail. So much, so obvious. In Germany it’s Die Schwanzmeise, which literally translates as the “tail chick”…which perhaps hints at why Americans call tits chickadees and indeed in French, the long-tailed tit is known as la mésange à longue queue, the long tail chickadee.
However, A caudatus is not a member of the Poecile genus like the Carolina chickadee, Black-capped chickadee, Mountain chickadee, etc. In North America many of the tit-like birds are chickadees, but they do have some of the same Poecile species as we have in the UK: Marsh tit and Willow tit, for instance. Wikipedia suggests that the term chickadee derives from the call made by the birds “chick-a-dee-dee-dee”. But that sounds like a reverse engineered explanation to me, better ask Mr Fields.
Bush tits, babblers and long-tailed tits…