What is the mnemonic reason behind b being galactic latitude? (in the Galactic Coordinates frame) I'm not sure if this is a question that has been posted before, and I'm also not sure if the answer is really mnemonic. If that's the case, I'd like to understand why we assigned $b$ to latitude anyways, so my brain can remember it more easily.
Thanks!
Länge und Breite are the German words for longitude and latitude. Thus 'b' seems like a natural choice for latitude and 'l' for longitude. A century ago when traditional choice of variable names were chosen by vote of feet, a reasonable amount of research papers were still published in German or people with some form of fluency in German. At the same time it's distinct enough from the variable names used in other coordinate systems which also have longitude and latitude (like the terrestrial where $\lambda$ and $\theta$ are commonly used), so the cause for confusion is reduced - even when you don't know German.