The word "most expressing" is correctly spelled using the IPA phonetic transcription /ˈmoʊst ɪkˈsprɛsɪŋ/. The first syllable is pronounced with the long 'o' sound, while the second syllable is pronounced with a short 'i' sound. The stress is on the second syllable, which is marked with the apostrophe following the 'k'. The final syllable is pronounced with a short 'e' sound, followed by the 's' sound in 'sing'. The spelling of this word follows English phonetic rules and helps to accurately express its meaning.
"Most expressing" is not a word in English, and there is no available etymology for it. "Most" is a superlative form used to indicate the highest degree of comparison, while "expressing" is the present participle form of the verb "express", meaning to convey or communicate a thought or feeling. When used together, they often appear in a sentence structure like "most expressing [something]", where "most" intensifies the act of expressing. However, they are not directly related to each other in terms of etymology.