Daniel Cassidy, in his crazy affront to the world of linguistics, How The Irish Invented Slang, claimed that the phrase spick and span comes from Irish spiaca’s bán. It doesn’t, of course. Let’s look at the evidence from Irish about the supposed term spiaca’s bán and then the evidence from English about the known origins of this phrase.
Does the term spiaca’s bán exist? As usual with Cassidy, there is absolutely no evidence that it does. Cassidy did not open a grammar book or a dictionary and find the phrase spiaca’s bán in it glossed as spick and span. He found two words in a dictionary and put them together to make a suitable phrase. The two words which make up the phrase do exist, of course. Spiagaí is a word meaning brilliant or gaudy, and it has an alternative version spiaca which is used in some dialects. Bán means white. So the phrase means ‘brilliant white’, which is not really what spick and span means.
However, there are also very good reasons for regarding spiaca’s bán as impossible, or at least highly improbable. Firstly, while Irish speakers sometimes put ‘s or agus between adjectives these days (because of Béarlachas or the influence of English), this is not traditional in the language. A big red book is leabhar mór dearg, not leabhar mór agus dearg. It is unlikely that an Irish speaker centuries ago would have done this. Secondly, when there are pairs of adjectives like this, it is almost always the case that the one-syllable word comes first. Thus we have tinn tuirseach, dubh dóite, deas néata, beag bídeach. It would really have to be bán spiagaí, which obviously isn’t going to be the origin of spick and span.
As for the English, the term spick and span has been in the language for hundreds of years. It is found in Sir Thomas North’s translation of Plutarch’s Lives, 1579: ‘They were all in goodly gilt armours, and brave purple cassocks apon them, spicke, and spanne newe.’ Apparently ‘new’ was nearly always added to the phrase in these early references. Most dictionaries suggest that the word spick is a variant of spike or nail, and span is an ancient term for a chip of wood, so the idea is that everything is new in an item, including the wood and the nails. Sounds reasonable to me. In any case, how many Irish speakers were living in English-speaking communities in 1579 and so even if the Irish phrase existed, how could it have been transmitted from Irish to English back then?