The spelling of the word "moone" used to be common during Middle English. The extra "e" at the end of the word indicates a long vowel sound, which is represented by the phonetic transcription /muːn/. However, this spelling is no longer in use in Modern English, and the correct spelling of the word is "moon", with a single "o" and no "e" at the end. The word still has the same pronunciation, /muːn/.
The word "moone" is derived from the Old English word "mōna", which is itself derived from the Proto-Germanic word "*mēnōn". This ultimately traces back to the Proto-Indo-European root "*mēh₁n̥s", which means "moon". The word has undergone various changes in spelling and pronunciation throughout its history, eventually evolving into the modern English term "moon".