Ἐρετρικοῦ

Morpho works with a static database. If you like, you can compare the output of Morpheus.

Parsed as:

✓ proper-name adjective masculine genitive singular (cp Ἐρέτρια)
proper-name adjective neuter genitive singular (cp Ἐρέτρια) of Ἐρετρικός