Boyao or Boyau: How To spell?

The word Boyao is misspelled against Boyau, a noun meaning "A winding or zigzag trench forming a path or communication from one siegework to another, to a magazine, etc."

Word ends with consecutive vowels 'AU' preceded by alphabets 'boy' is misspelled as 'AO'
Wrong Spelling:  boy-ao 
Correct Spelling:  boy-au 
Find more incorrect spellings of Boyau to spell right way.

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