It's the language of the interior world, of course. 😄
As someone who has spent his life studying languages and linguistics, I can offer the confident informed opinion that there is almost certainly no human language characterized by words with long stretches of vowels. (But one must always be prepared to be surprised.)
This quotation is from a ancient magical text, and Crowley undoubtedly included it K.O.P. because it amused him to attribute something so seemingly nonsensical to Jesus, opposite a New Testament quote attributed to "Anonymous".
This long word was probably written down in the Greek alphabet (maybe Coptic?). The vowels should be pronounced as in Spanish or Italian (or almost any European language except English). I bet that Ō with a macron is not supposed to be a long O, but rather to represent the Greek letter Omega, as distinct from the Omicron represented by O. They should be pronounced the same ("oh" to rhyme with "hoe"). Likewise, Ē (with macron) and E are probably Eta and Epsilon, and can be pronounced "ee" (rhymes with "see") and "eh" (like the vowel in "bet"), respectively. KH is probably Chi, pronounced like the German "ch" in "Bach" or the Scottish "loch"; TH is probably Theta, pronounced like the "th" in "theta".
I would recommend -- but my advice here is no better than anyone else's -- pronouncing "AAA" as a very long "Ah", while mentally counting to three. It's a fun word to say.
Have fun in the interior world, and remember to take lots of pictures to share with us.