>>24570835
Yeah these are called nomina sacra. They are hugely common in Orthodox manuscripts and mosaics, including Greek but also Old Church Slavonic. They could even inflect.
>Θεός ΘΣ ΘΥ
>Κύριος ΚΣ ΚΥ
> Ἰησοῦς ΙΣ ΙΥ
>Χριστός ΧΣ ΧΥ
>Υἱός ΥΣ ΥΥ
>Πνεῦμα ΠΝΑ ΠΝΣ
>Δαυίδ ΔΑΔ
>Σταυρός ΣΤΣ
>Ἄνθρωπος ΑΝΟΣ
>Πατήρ ΠΗΡ

Pic related is
>Ἰησοῦς Χριστός
>ἡ χώρα τῶν ζώντων (metaphorically qualifying Jesus as the land of the living)