The spelling of the word "most again" closely follows its phonetic transcription in IPA: /moʊst əˈɡen/. The first syllable is pronounced with a long "o" sound and a soft "s" sound, while the second syllable is pronounced with a schwa sound and a hard "g" sound. The spelling of "again" also follows the typical English pronunciation, with a soft "g" sound and a weak "n" sound. Together, these phonetic elements create the proper spelling for the phrase "most again".
The phrase "most again" does not have a specific etymology. It appears to be a combination of the words "most" and "again", where "most" is used as an intensifier and "again" means once more or another time. The word "most" originated from Old English "mǣst", which means greatest, most, or almost, while "again" comes from Old English "onǣġen", meaning in return or back.