> * According to OED the reason that some animal names have the same singular and plural was that they originally contained a long vowel, e.g. deer, sheep, fish

> * According to OED the reason that some animal names have the same singular and plural was that they originally contained a long vowel, e.g. deer, sheep, fish. Turns out, horse was also in this group but after a sound change its vowel shortened, hence the -s plural now. I learnt that by reading The Wee Free Men by PTerry: "Aye, it's no' that good for the ship, havin' tae drink oout o' that pond after we've been bathing. It's terrible, hearin' a ship try tae spit." (When in doubt, assume the more "dialectal" pronunciation is the older one. Though I think the wee free men actually overdo it and pronounce plural ship too.)