Greek would be a better guess than Cyrillic but the shape of the majuscule 'e' and 's' together with the context make it more likely the top-left text is Coptic and not Greek. Top right is Aramaic and under that Arabic, all three just say 'pentecost'. These are the liturgical and everyday languages of the Coptic and Syriac Christians of the Middle East. It's not an icon but it it is drawn in the Eastern Christian style. As such Cyrillic wouldn't be out of place either, as used by the Russian, Bulgarian, Serbian etc orthodox churches.

Since you know it's depicting the Pentecost, I'm not sure what you want explained beyond that, if anything? 12 apostles, Virgin Mary, holy spirit descending, represented as a bird.. the imagery isn't specific to eastern Christianity even if the rendering of it is.