"Cor cordium"
It means "heart of hearts". There appears to be a reference to the heart of the poet Shelley: his tombstone had COR CORDIUM on it, as if his heart as an inspired young revolutionary was a totally special heart. His actual heart was cut out and preserved before burial, and was kept by his wife Mary Shelley. If someone is asking about your cor cordium, they want to know who you are really, what you really want, what you really intend, under all your masks and guises and all the sacrifices you make and the suboptimal substitutes you accept. What is it you’d do, want, be, if you had your druthers and feared no judgment and nothing internal or external impeded you, including the limits of your own nature? That’s what’s in your “heart of hearts". But also, phrases like cor cordium, rex regum, dominus dominorum, i.e. heart of hearts, king of kings, lord of lords, have a whole penumbra of possibilities and they mean a heart/king/lord higher or more valuable than allother hearts/kings/lords.
