The spelling of the word "ashier" is a bit tricky. It is pronounced /ˈæʃiər/ and is derived from the word "ashy", which means covered in or resembling ashes. The '-ier' suffix is commonly used to form comparative adjectives, indicating that something has more of a certain quality than something else. In this case, "ashier" means more ashy. While the spelling may seem unusual, it follows the pattern of English suffixes and is essential in communicating meaning.
* The statistics data for these misspellings percentages are collected from over 15,411,110 spell check sessions on www.spellchecker.net from Jan 2010 - Jun 2012.