em-pinada
Hyphenation is done by TeX, and the patterns are loaded based on the
@documentlanguage. If your plain TeX format does not include Spanish
hyphenation patterns, which appears to be the case, nothing can be done.
If you send a runnable .texi file and the resulting .log file, perhaps
more could be discerned.
For me, the following simple document shows the (presumably) correct
hyphenation of em-pi-na-da; if I comment out the @documentlanguage, so
that the standard American English hyphenation patterns are used, I get
emp-inada. (@showhyphens is a plain TeX command, not Texinfo, but it
doesn't matter for our purposes here.)
\input texinfo
@documentlanguage es
@showhyphens{empinada}
@bye
Best,
Karl
