In TeXForm#
TeXForm parses this entry as a character leaf mapped to U+03B7 (GREEK SMALL LETTER ETA).
\bbalpha\bbbeta\bbchi\bbdelta\bbDelta\bbdotlessi\bbdotlessj\bbepsilon\bbeta\bbgamma\bbGamma\txtbfbbeta
\txtbfbbetaSymbol
The η symbol (Greek small letter eta, U+03B7), written as \txtbfbbeta in LaTeX text mode.