Font problem

Greetings, running on Xubuntu 16.4 I'm currently still using XEmacs 21.4.22 which is the version officially provided by Xubuntu (I have yet to have the spare time to compile XEmacs directly from the Mercurial repository ... sigh)-: Whenever I start XEmacs I receive the following warning message: Warning: Cannot convert string "-*-helvetica-bold-r-*-*-*-120-*-*-*-*-iso8859-*" to type FontStruct In my "~/.Xresources" file I have several fonts specified for quite a few Xemacs resources, but I'm not using any "helvetica" font. So I'm assuming XEmacs is falling back to some default here for some resource I did not specify. Since it's a bold font, it's probably for some weird menu I'm not even using ... In file "/etc/X11/fonts/misc/xfonts-base.alias" I found the following line: variable -*-helvetica-bold-r-normal-*-*-120-*-*-*-*-iso8859-1 so XEmacs could also use "variable" as a default for some unspecified resource. If somebody could point me to the resource name associated with that de- fault font in XEmacs, I could update my "~/.Xresources" file according- ly, get rid of this annoying warning message, and would again be very happy :-) Sincerely, Rainer