Etymology tree Proto-Indo-European *ḱerd- Proto-Indo-European *ḱḗr Proto-Indo-European *ḱr̥díyeh₂ Proto-Hellenic *kərdíyā Ancient Greek καρδία (kardía)lbor. English cardio- Proto-Indo-European *gerbʰ- Proto-Hellenic *grə́pʰō Ancient Greek γρᾰ́φω (grắphō) Proto-Indo-European *-mn̥ Ancient Greek -μᾰ (-mă) Ancient Greek γράμμα (grámma)lbor. English -gram English cardiogram From cardio- + -gram.