The current create-name implementation will generate all alphabetic strings starting with "w" which includes "wm" after only 12 new toplevels. This overwrites the global command "wm" which is kind of important.

On a side-note, I personally think the encode-base-52 is a bit overengineered vs ~36R but that's not a bug so I didn't include it in this patch. ~36R wouldn't have stomped on any existing globals by the happy accident of it using UPCASED letters only.