A strange word, or rather two strange words. The first is encountered only in the phrase court of cassation, referring to a French supreme court of appeal, and it’s pretty straightforward: it’s from Latin cassa¯re ‘to bring to nought, annul’ (: cassus empty, void), also the source of the verb quash, and such a court quashes decisions of other courts. The other word refers to ‘a piece of instrumental music of the eighteenth century similar to the serenade, and often performed out of doors’ (OED), and it can be traced back only to Italian cassazione. Willy Apel’s Harvard Brief Dictionary of Music says “The name may be derived from It. cassare, to say farewell, or from L. gassatim, streetlike,” but my Italian and Late Latin books know no such words. And yet it has such an open, transparent look: what, me obscure? And such a useless word, too, given the equivalent divertimento. But I like it. There’s something so old-fashioned and Old World about it.