Modern Greek, right? μωρό, moro. And yes it is, though you have to say “my baby”, μωρό μου moro mu.
The ancient Greek term it comes from had a final n. Why yes, the modern Greek word for “baby” is the Ancient Greek word moron. In Bithynian Greek, the word for baby is σαλό salo, which is the word for holy fool—same thing.
Added bonus: the masculine vocative of moron is μωρέ more. This is a Balkan-wide vocative particle, and it just means “hey”; typically, it’s reduced to vre, or in Greek re.
Why yes, everyone in the Balkans is calling everyone else a moron just to get their attention.
The feminine vocative is μωρή mori. Unsurprisingly, the feminine vocative is not neutral like more is.
Added bonus: the Elizabethan English for baby is fool. As Polonius used it in Hamlet.