"Θηριακλού μου" (Theriaklou mou) in Greek translates to "My Theriacos" or "My little Theriacos".
"Θηριακός" (Theriakos) is a name, often a diminutive of a longer name incorporating that root. The "μου" (mou) is a possessive pronoun meaning "my". So it's a term of endearment, similar to saying "My darling" or "My sweet [name]".