"Most subitaneous" is a phrase that is rarely used in everyday conversation, but it can be seen in literature or academic writing. The word "subitaneous" means sudden or abrupt, and it is pronounced /səbɪˈteɪniəs/. The spelling of this word can be easily broken down using the International Phonetic Alphabet (IPA), where the syllables are pronounced as follows: "suh-bit-AY-nee-uhs". Overall, the spelling of "most subitaneous" is straightforward and can be understood by breaking down the pronunciation of each word.
The word "most subitaneous" does not have a clear etymology as it appears to be a combination of two unrelated words. "Most" is a superlative form of the adjective "more", which comes from Old English "māra". "Subitaneous" is derived from the Latin word "subitus", meaning sudden or unexpected. However, it is worth noting that "subitaneous" is not a commonly used English word and may have been coined or modified for a specific purpose.