The correct spelling of the word is "most vulnerable". The incorrect spelling of "most woundable" likely comes from mishearing or misreading the word. The IPA transcription for "vulnerable" is "ˈvʌlnərəbl", with the stress on the second syllable. This word derives from the Latin "vulnerabilis", meaning "able to be wounded". While it is understandable how the mistaken spelling may have come about, it is important to use the correct spelling to ensure clear communication.
The word "woundable" is not commonly used in modern English. However, its etymology can be traced back to the Old English word "wundian" which means "to wound" or "to injure". This Old English word ultimately comes from the Proto-Germanic word *wundōną, which has the same meaning.
The word "most" is a superlative form indicating the highest degree of something.