After an entire weekend spent scouring every corner and cranny in your apartment, you might describe the place as spick-and-span: so gleamingly clean it seems new. In fact, the full phrase actually is spick and span new—though unless you’re an etymologist, that may not shed any light on where the term actually came from.
Before we had spick and span new, we had span-new, a word dating at least as far back as the early 1300s. According to the Oxford English Dictionary, it derives from the Old Norse term spán-nýr, with nýr meaning new, and spán meaning chip (as in wood chip). Basically, as Pascal Tréguer explained on his word histories blog, span-new meant “as new as a freshly cut wooden chip.”
Spick, meanwhile, is believed to come from a number of old words that all mean nail—words also thought to be related to spike. There’s the Middle Swedish spijk, the Dutch spijker, and the Old Norse spik (which more accurately means splinter), to name a few. In Dutch and Flemish, people used the expressions spiksplinternieuw and spikspeldernieuw in pretty much the same way span-new was used in English: to describe something so spotless it must have just been made. Such as “a ship that was freshly built, so with all-new nails and timber,” as Michael Quinion wrote on his blog World Wide Words.
Somewhere along the way, English speakers blended those phrases with span-new to create spick and span new. The first person to do it in writing (that we know of) was Sir Thomas North, whose 1579 translation of Plutarch’s Lives of the Noble Grecians and Romans featured this line: “They were all in goodly gilt armours, and braue purple cassocks apon them, spicke, and spanne new.”
Eventually, the new got dropped. And the first person to do that in writing (again, that we know of) was Samuel Pepys, who wrote in a 1665 diary entry that his acquaintance Lady Batten was “walking through the dirty lane with new spick-and-span white shoes.”
Though the phrase did originally refer to things that really were new, the definition loosened up over time. These days, calling something “spick-and-span” doesn’t necessarily mean it’s never been used—just that it looks that way. Brand-new, on the other hand, still literally means new. But the brand in question isn’t referring to stores or companies.