Whole nine yards
This relatively modern American expression from the 1960s meaning ‘all the way, completely, everything, the whole lot, the works’ is one of the most talked about and written about etymological conundrums. It still remains the Holy Grail for American etymology. There are many different theories, but the fact remains no one knows who coined the expression or on what basis. Recent discoveries of citations for six or seven yards from as far back as 1912 indicate that the number of yards is probably irrelevant, which weakened all those theories that focussed on the long-time mystical fascination with the number nine - why there are nine Muses and why a novena is nine days of prayer etc. The search is still on. Academics, journalists and many etymological researchers are still sifting through records facilitated by digital search engines, trying to nail down the origin but it still remains unsolved.