Not all nouns follow simple rules when transitioning from single to plural form.
Plural of roof and hoof.
Hoofs is a much older rendering of the plural form of hoof.
Dwarf dwarves elf elves hoof hooves roof rooves.
Hoofs is also a plural form of hoof the horny part of an animal s foot.
On the other hand spoof simply adds the plural s suffix to become spoofs.
For a good 250 years hoofs was the primary plural form of hoof analogized with the word roof which has roofs as a plural form.
And just like roof hoofs was the dominant one.
But at the same time there are several exceptions form this rule.
When at school i was taught that the plural of roof is rooves and the plural of hoof is hooves.
When to use hooves hooves is the newer and now more common plural form of the hoof.
Should it become rooves like hooves.
It wasn t until the last 40 50 years that hooves began to pick up steam.
But hooves woke up in the 20th century and by about 1970 it overtook hoofs in usage and that s where it has stayed.
This is exactly how hooves is obtained as the first plural of the noun.
Maybe my teachers were wrong.
Hoof comes from the old english word hof.
And this is how you get hoofs.
Poof and poofs follow the same rule.
Just like roof hoof also started with two plural forms hoofs and hooves.
The plural form of hoof is hoofs or hooves.
The plural of hof is hofas which when pronounced would have sounded like hooves.
Hoof for instance becomes hooves in the plural.
I was taught rooves in grade school on the east coast.