The word savoiardo literally means from Savoy, a region of France that in times gone by included parts of the Italian region of Piedmont. The County of Savoy in time became a Duchy. Later on, the Duke of Savoy acquired also the title of King of Sardinia and finally, in 1861, Vittorio Emanuele II became King of newly-united Italy. The Savoy family lost the Italian throne in 1946, when people voted to change the monarchy into a republic.
The savoiardo of interest in this context is a cookie and, as its name suggests, one related to the noble family of Savoy. The story I read says that in the mid-14th century the pastry chef of Amedeo VI (a.k.a. the Green Count) created a feathery, finger-shaped cookie for a dinner whose special guest was the King of France. The cookie was a big success and continued its life graced with the blessing of the noble family under whose roof it was created.
Savoiardi (as usual, the plural form is much more used than the singular) can be eaten as they are, but in practice they are more often used as ingredients of desserts, thanks to their delicate flavor, lightness and sponginess. Tiramisu, zuppa inglese and charlotte russe are three examples of desserts that employ savoiardi as supporting cast.
[I was inspired to write this post by Julia's beautiful charlotte russe, for which she baked the savoiardi.]