|Some nice hice in San Francisco|
"Mouse" was mus in Anglo-Saxon. Way back, when the Anglo-Saxons first arrived in England, its plural was musiz (pronounced moo-seez). Just as with "goose", the sound in the second syllable affected the first syllable (the phenomenon called "i-mutation"). Whereas gosiz became ges, musiz became mys (pronounced "meese"). With the Great Vowel Shift, this became the "mice" that we know today.
The Anglo-Saxon ancestor of "house" (hus), however, belonged to a category of noun, like the ancestor of "deer", where the form was the same in the singular and the plural. One hus, two hus. So there were no husiz to precipitate the i-mutation that would have led eventually to a plural "hice".
Two house, two housen, two houses?
The unchanged plural "house" (one house, two house) actually survived into the 14th century, but it was ultimately defeated by two other possibilities. One was an irregular plural "housen", which still survives in some dialects. Inevitably, though, the strength of the regular "add (e)s to make the plural" pattern in English gathered "house" to its ample bosom and "houses" was the ultimate winner.
But, just to make life difficult for ESL learners, we added a subtle pronunciation change to the plural. Whereas the "s" in "house" is pronounced with a hissing "SS" sound, without the vocal cords vibrating, that same "s" in "houses" is pronounced like a "z", with the vocal cords vibrating. (If you put your hand on your throat and hiss a "ss" followed by a "zz" you can feel the difference).
This phenomenon is caused by the fact that the consonant is between two vowels, and to utter a vowel, you HAVE to vibrate your vocal cords, so it's easier to keep vibrating them for the consonant in the middle as well. This voicing of consonants between vowels (intervocalic consonants) has existed in English since the earliest times.
T becomes D, F becomes V, S becomes ...
We North Americans voice our intervocalic t's (e.g. "tutor" sounds like "Tudor"), and English has many words where an unvoiced "f" becomes a voiced "v" in the plural where the "e" following the "f" used to be pronounced: wife/wives, half/halves, leaf/leaves, life/lives, loaf/loaves, and so on. With those, at least we indicate the change in sound by the spelling. But "houses" is the only example in standard English of a plural where a voiceless intervocalic s becomes voiced. Think of words like "buses", "asses", "cases", "bases", "cabooses" (no, the plural is not "cabeese"!) and so on.
HOUZes or HOUSSes?
Being the sole example of a pronunciation phenomenon in the language is not good for phonetic job security. Inevitably the predominant regular pattern will start influencing the irregular one. And indeed, a reader from Michigan informs me that her children (in their fifties) pronounce "houses" with a voiceless ss sound, that is, "HOUSSez", although she herself says "HOUZes". I conducted a poll of my facebook friends, and of 73 who responded, only one, from Ohio, said "HOUSSez". Nonetheless, Merriam-Webster dictionaries include both pronunciations for the plural, and there is chatter on the Internet about the voiceless version (complaining about it, naturally). I cannot for the life of me understand why people get so upset about slight pronunciation differences.
How do YOU pronounce "houses"?
For more information about mouse-related words (not to mention some titillating pictures), see this post: http://katherinebarber.blogspot.ca/2012/08/of-mice-and-men.html
For some more examples of voiced intervocalic consonants, see these posts:
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