Obscure message in Frescobaldi

[Hajo Baess]

This is not about a Lilypond problem, strictly speaking, but it is
related indirectly, and since here there are very many LilyPond users
around here, I also hope to address at least a couple of Frescobaldi
users here with an unanswered question, hoping that someone can solve
this for me:
I am localising Frescobaldi, and I am stuck with an obscure message
which I have never seen using it. It says:

Clear Grab

Since it is hard to translate something you don't understand: what is
this about? What is the context? What has been grabbed and can be
cleared? 

The message entry can be found in the messages.py file in the i18n
folder of Frescobaldi:

> _("QShortcut", "Clear Grab")

Thanks a lot for any suggestions to help me understand...