Grad means "castle" - comes from Graz, Austria - Gradec in Slovenne.
Which is, apparently, where my family name comes from.
Slav - Slave.
Slov - Slovenly.
What empires routinely pillaged this region and assigned the labels of its population? Where do Abramovic and Durdevic come from?
I do not know if this has anything to do with what Q meant by castle lock - but it is a little crumb of info and related stuff I have been looking into.