Many times the inscriptions are deliberately stylized...
Here there is the mixing in of upper case letters and capitals that are like large versions of also stylized lower case letters. Deciphering some more:
The initial H is a capital eta with the rough breathing mark, classical pronunciation (used throughout here, not modern Greek) = hay = hē, the definite article, that is
The (feminine, singular, nominative). The next word has the Greek letters that transliterate as
aGia but the expected rough breathing mark is not included, perhaps stylistically it's understood and if so gives
hagia (rather than
agia) = holy (fem, sing., nom). The name has the initial letter alpha as a stylized large lower case letter. The smooth breathing mark is on the second vowel of the initial diphthong, the convention for non-capitals. If the initial alpha were a capital, the breathing mark (and accent, though not in this case) would have been, if written according to convention, before the initial capital letter, thus Ἀι. This gives the transliterated name,
aikaterina, and using caps as on the icon,
aikaTeRiNa. So the transliterated name is Hē' hagi'a aikateri'na
, The holy Catherine. Here is the Greek where I've given the other case of the letters and include the missing breathing mark.:
Ἡ ἁΓία αἰκαΤεΡίΝα
ἡ γ Α τ ρ ν
Ἀι
Putting
the holy catherine into Google translate gives the modern Greek as
η αγία Αικατερίνη
i agía Aikateríni.
