\tenrm
LaTeX 2.09 defined a large set of commands for access to the fonts
that it had built in to itself. For example, various flavours of
cmr
could be found as \fivrm
, \sixrm
, \sevrm
,
\egtrm
, \ninrm
, \tenrm
, \elvrm
, \twlrm
,
\frtnrm
, \svtnrm
, \twtyrm
and \twfvrm
.
These commands were never documented, but certain packages
nevertheless used them to achieve effects they needed.
Since the commands weren't public, they weren't included in LaTeX2e; to use the unconverted LaTeX 2.09 packages under LaTeX2e, you need also to include the rawfonts package (which is part of the LaTeX2e distribution).