diesis definition by Webster's New World
Origin: Classical Latin ; from Classical Greek ; from diienai, to send through ; from dia-, through plush hienai, to send: see jet
diesis definition by American Heritage Dictionary
noun pl. di·e·ses
Origin: Medieval Latin, semitone (which was indicated by a double dagger), from Latin, quarter tone, from Greek diesis, a letting through, from diīenai, to send through : dia-, dia- + hīenai, to send; see yē- in Indo-European roots.