[QUOTE=CalMeacham]
The word “pea” was actually back-formed from the ostensible plural, “pease”, which is never used anymore (now everyone writes “peas”, unless they’re quoting the nursery rhymes about “pease porridge”).
[/QUOTE]
Both “pease” and “cherries” were originally collective nouns, I believe. The modern singular forms “pea” and “cherry” are back-formations
I looked at the word henchman once and wondered what a hench was. So I looked it up. Hench was from an old German word meaning stallion.
I’m guessing that your henchman was the groom who was strong enough to control the stallion, and he could be called on for other things requiring strength.