The first computer mouse (1964) The English word mouse has been around longer than the English language has. Its origin is in the Proto-Germanic word m ū s , which is also a word for the rodent. It gave rise to the Old English mous and mowse , the German Maus , and the Dutch muis . The reason the word has the peculiar plural form of mice is due to a process known as cheshirization, where a change in the way certain sounds in a language change, but an obsolete phonological distinction gets reclassified as a new form. To make this simpler, mice is descended from the Proto-Germanic m ūsiz, which is the form of the nominative and vocative declensions of m ūs . You need not know what a declension is, except that the vocative declension no longer exists in English (not as a distinct, marked form, at least). The only way a declension changes the modern English word mouse is when we use the possessive declension mouse’s . Declensions are something you n