footnoteGrob allowed Grob names

[Jan-Peter Voigt]

Hello list,

I am now using lilypond 2.14 and have a question to the newly introduced 
\footnote command:
What grobnames are allowed?
The following works as expected:
--snip--
\relative c'' {
    \footnoteGrob #'NoteHead #'(1 . 1) \markup { \super "*" } \markup { 
\line { \super "*" my explanation} } c
    \footnoteGrob #'Rest #'(1 . 1) \markup { \super "*" } \markup { 
\line { \super "*" my explanation} } r1
}
--snip--

But the following does not expose a footnote:
--snip--
\relative c'' {
    \footnoteGrob #'MultiMeasureRest #'(1 . 1) \markup { \super "*" } 
\markup { \line { \super "*" my explanation} } R1
}
--snip--

And is there a way to use footnotes in lyrics?

Cheers, Jan-Peter