Years ago, former NYT columnist William Safire wrote an article for his column about language and grammar in which he asked for a word to explain an in-law in-law relationship. Readers wrote in with ideas. He wrote that one reader had suggested the Spanish word "consuegro." Since that word was in a foreign language, Safire opted to use the Yiddish word, "mechutan" as there is no counterpart for the word in English.
A New York Times article about the revival of Yiddish has taught me the derivation of the expression bubbe mayseh. Live and learn.
As in a university, some teachers are particular draws. Michael Wex, a Canadian author and philologist, taught one group about the derivation of the term bubbe mayse — literally “a grandmother’s fable” but an expression used for any implausible tale. It was, he revealed, based on a 16th-century chivalric story about a Christian knight named Bovo who improbably marries a princess under a chupah — a Jewish wedding canopy — and arranges a circumcision for twin sons. Over time, few Jews were familiar with Bovo, so the expression morphed into something said by a bubbe.
Read full article: http://www.nytimes.com/2010/11/26/arts/26klezmer.html?src=me&ref=general