If I google for list of X11 window managers "xwm", there's a reference in the first hit. The quotes around xwm are useful to screen out false positives.
oh god. commence operation “spam the random name generator”!
Taking a closer look at the original xwm, this project has long since been dead. i wonder if it would be fair to say the acronym itself could be used, as tribute to the original? or is that too confusing?
Any other advice for checking for naming conflicts? I used github, google and repology.org and was excited when I saw no hits on the name. =S