These exceptions to the rule are hypothesized to have originated from the roots originally having contained a phoneme no longer present in modern Hungarian, the unrounded back vowel , or its long counterpart . It is theorized that while these vowels merged with or , less commonly or , the vowel harmony rules sensitive to the backness of the original sound remained in place. The theory finds support from etymology: related words in other languages generally have back vowels, often specifically unrounded back vowels. For example, "nyíl" 'arrow' (plural "nyíl-ak") corresponds to Komi ньыл , Southern Mansi .