What primary school student hasn’t been correctly at some point for saying “fastly”? I know I was…and I know I’ve done the correcting too. But last week when my son said something about this, my husband and I decided to look it up (because really, why isn’t that a word??).
Pretty interesting discovery too!
So the original meaning of fast, dating back to the 12th century, was “firmly, securely.” We still use this occasionally, though it’s old-fashioned. “It stuck fast” etc. Early on, fastly was then indeed a word and used in relation to this sticking definition. It didn’t go completely out of use until the 19th century.
So where did the notion of “quickly” come from? Well, that meaning has been around nearly as long as the original, and came about rather organically. Etymologists believe it’s because “to run hard” and “to run quickly” mean the same thing–and also perhaps because if you’re running “fixedly,” you’re keeping up with anyone in front of you.
Regardless of how it evolved, it’s certainly worth noting that fast was used both as an adjective and an adverb since the get-go, with that “fastly” fading from use a couple hundred years ago solely because the root word had been treated as both adj and adv for so long.
So sorry, kiddo. No need for that -ly. 😉