твр̏доко̄ран (Serbo-Croatian) comes from Serbo-Croatian ко̏ра, from Proto-Slavic kora, from Proto-Indo-European ḱer-, from Proto-Indo-European kr̥-, from Proto-Indo-European ker- — army.
твр̏доко̄ран (Serbo-Croatian): obdurate, stiff, stubborn