Again Anatoly Vorobey has an Avva post (in Russian) that tickles my linguistic fancy. It concerns the Hebrew word for ‘testicle,’ אשך, which according to Anatoly is pronounced a-SHAKH (אָשָׁךְ) by practically all speakers of Modern Hebrew but which all reference works claim is E-shekh (אֶשֶׁךְ), which is indeed given in my dictionaries and at Wiktionary. As he says, the origin is obvious: since the word is generally used in the plural, asha-KHIM (אֲשָׁכִים), the singular came to conform with it. He finishes his post thus:
Why there isn’t a single normal/decent Hebrew dictionary that describes the language the way people actually use it (I repeat once again – this isn’t about colloquialisms or slang! even in a “lofty” context, people only know and use the word ashakh!) remains a mystery to me. And that’s annoying.
It reminds me of my puzzlement as to why нарды (nardy), the normal Russian word for ‘backgammon,’ isn’t in the dictionaries.
Incidentally, the post is called “ашах! как много в этом слове” [ashakh! how much is in that word], a takeoff on a famous Pushkin passage (from Eugene Onegin) that goes “Москва… как много в этом звуке Для сердца русского слилось!” [Moscow… how much is blended in that sound for the heart of a Russian!].
Various Oti-Volta languages have paired-body-part words where the singular has been remodelled after the plural form too (“leg” in Agolle Kusaal, and “ear” in quite a number of languages. Not “testicle”, though.)
I don’t remember if I’ve heard the word pronounced (only beitsá, lit. ‘egg’), but this sounds right. eshekh sounds awfully correct to me (though I myself might use it, among other archaisms).