Woah Vicky Tattoo Removal Hollywood Actress

Often, wow is positive and whoa is negative. Wow is a reaction to a big surprise (i am impressed), and whoa means please stop (which maybe due to my surprise. ) however, with irony, i can. The oed lists woah as a variant of woa which is a variant of whoa i don't remember ever seeing the woah spelling (i'd want to pronounce it as two syllables:

How do i spell the word woah as used in surprise or excitement? Is it similar to wow except for the last w? Some dictionaries define whoa as stop! While some define it as an expression of surprise/astonishment. Is there such a word as whoa, where did it originate from and what is its.