Seems to be a lot of language freaks here. Nobody ever told me why ‘-s’ is used as a plural in English, French, Spanish, Portuguese and part of Dutch, though it is not a common plural suffix of either the Germanic or Romanic branches of the Indo-European language family. Did it come from the genitive form ‘-es’ used in Germanic languages? It’s not in Old English / Anglo-Saxon, is it?
Ray
Well, I’m pretty sure Old English (anglo-saxon) used the germanic -n for plurals, ala “oxen” and “children.” As for the s, it most likely came from the Norman French introduction that led to the formation of the modern language.
Jason R Remy
“No amount of legislation can solve America’s problems.”
– Jimmy Carter (1980)
So where did the French (Franks, Gauls, whatever) get it? From some local non-Indo-European language? Latin didn’t use it.
Ray
NanoByte claims:
Well, actually, that’s not entirely correct.
“Kings die, and leave their crowns to their sons. Shmuel HaKatan took all the treasures in the world, and went away.”
Darn, hit the wrong key; I was actually going to explain my retort 
It’s true that nominative plurals of words in the a- and o-declensions are not formed in “-s”; hence feminae, “women”, viri, “men”, saxa, “rocks”. However, oblique plurals often do end in -s; feminis, “women” (ablative), viros, “men” (accusative), saxis, “rocks” (dative). In most modern Romance languages, we find not only a reduction of the rather complex Latin declensive and grammatical structure into the simple masculine/feminine opposition, but also a reduction in the case structure to nominative/genitive (and sometimes an accusative, or generic oblique, case). Unless we are to demand that nominatives in modern day languages inherit only from nominatives in their ancestors, we can’t disallow plurals ending in “-s”.
It’s also true that adjacent languages affect each other, no more so than when the two languages are sitting atop one another. Gothic and Old German have long since vanished. In the first case, Gothic was replaced by Castilian, Catalan, and Provençal; in the latter case, not only by French, but by English, Dutch, High and Low German, and Yiddish.
In the case of English, in was affected, not only by the Norman Conquest, but also by Danish/Norse conquest and settlement, and by the intrusion of Germanic conquerors and settlers into a Celtic milieu. Had the Saxon forebears of the English stayed in Hanover, their dialect might have remained more complex; as it was, creolization reduced it to as simple a form as could be derived from Old German whilst remaining unambiguous.
“Kings die, and leave their crowns to their sons. Shmuel HaKatan took all the treasures in the world, and went away.”
Actually, all masculine a-stem nouns in Anglo-Saxon do have nominative and accusative plurals ending in -as. That’s about 35% of all nouns in the language, so I’d guess that’s where our modern usage comes from.
Third declension masculine and feminine Latin nouns also have nominative plurals ending in -s (reges, urbes). Almost all Latin nouns (except neuters) have accusative plurals ending in -s.
I think I might be a nerd …