Blame it on drunk peasants! Isn’t that always the case? If you hold your hand in front of your mouth and say Very or Fairy – notice with Very you feel a little air. V’s are considered voiced, and F’s are considered voiceless (meaning no air). So it’s somewhat natural that it happened like this.
So the drunk peasants felt that the V sound sounded better with the plural S.
Plurals in English are odd. For instance, one child, two children OR one bird, two birds – sometimes and S and sometimes and N. More examples. 1 brother, 2 brothers, but also Brethren. Brethren was the old English word for ‘brothers’. It appears in the King James, so we still use it with religious stuff.
As a whole, the S is with English for plurals, and the N is with most other Germanic languages, German, Swedish, Norwegian – and it starts to change a little bit with Dutch. And in English BAM! Esses are everywhere.
The S in English for plural most likely was a French import from Billy the Conqueror who was all like ‘I am the rightful king of England so use the damn S!!” After all he was the new King and what he said, you did.
So the English peasant, drunk and confused, might have said ‘one loaf, two loafen’, were now required to say ‘one loaf, two loafs or loaVVVVes”!
Ain’t languages cool?