This Troublesome Pair was suggested to me by my husband. He’s good at coming up with these; I’m not sure how many have been suggested by him over the years. Both of these words mean an excess, but one just means “more” while the other means “too much!” There are some interesting archaic terms, too. For example, I always ‘knew’ that “King John died of a surfeit of lampreys” but I didn’t know exactly what that word meant, thinking it was standing for just “too much of” rather than a more specific meaning.*
A surplus is the amount that’s left over when you’ve met all your requirements. So if you have a bag of broad beans to cover every week for the next year and you will carry on with your next harvest once those are used up, anything over 52 bags is your surplus. In accounting terms, it means the positive difference between income/assets and expenditure over a period, so if I earn £100 from selling broad beans but spend £30 on bags to sell them in, my surplus is £70. And in even more specific accounting terms, it means the amount by which a company’s assets are worth more than the face value of its stock.
So a surplus doesn’t really carry the idea of TOO MUCH, whereas a surfeit is the “too much” one. It just really means an excess, but it isn’t really used in a positive sense (unless you’ve found examples – do share if you have). And in archaic terms, it was an illness that was caused by excessive drinking or eating – so King John’s “surfeit” wasn’t an excess of lampreys but the illness brought on by having eaten the excess of lampreys. If we go back to our broad beans, although it’s subjective, I’d say that having, for example, 104 bags of broad beans when you only need 52 would count as having a surfeit.
I do love these small distinctions. Interestingly, surfeit and surplus both come from Latin via Middle English (thank you, OED), so it’s not one of those cases where we have one Germanic and one Latinate word for the same thing.
And the obsession with vegetable produce? Blame the people who presumably have allotments and keep leaving courgettes out on walls and the pavement for people to take and runners to trip over / jump.
*Edited to add: Oh, deary me. I have been informed by reader Ian Johnston that “It was Henry I that died from a surfeit of lampreys, John fined the City of Gloucester for failing to deliver him a lamprey pie at Christmas; a dearth not a surfeit of lampreys”. Thank you to Ian for pointing that out and I stand corrected!