Herewith, my own definition:
To chase a rabbit - to follow a series of associations, particularly as they lead in unexpected directions. Particularly applies to rambling discussions.
The above is a pretty good metaphor for a bull session. Bull, of course, being short for bullshit, and both parts of that word have their roots and uses, both together and separate, and so forth. However, The Etymologicon: A Circular Stroll Through the Hidden Connections of the English Language by Mark Forsyth (AKA The Inky Fool) is a far deeper chase through brambles and weeds than I am competent to pursue. As the subtitle says, the work is circular, beginning and ending with the question of whether one can turn up a book (you can't).
Looking back, I find that the author could have closed the loop in a number of places. He is one who prefers to keep the rabbit running as long as possible, or at least until a specified word count is achieved. The 113 chapters cover 259 pages, plus another 19 of quizzes and other arcana. I think it most useful to pick 3 spots at random (and an easy cop out):
- p 27 – The phrase we find is letting the cat out of the bag, which actually has to do with someone trying to sell a pig in a poke (sack). You avoid being scammed by peeking inside, and seeing there is no pig, you let the cat out. But this was a side path in a discussion of archery, and the term point blank. No one should be surprised to know that blank in this case derives from blanc, or white in French. White is the color of the bullseye. If you are standing close enough to the target, you can hit the center without aiming high to account for gravity: you point right at it because you are at point blank range. The term bullseye is not followed, but could lead along an interesting path.
- p 58 – This begins a discussion of three names related to "justice", loosely construed, and their relation in particular to capital punishment. The names are Guillotin, Derrick, and Jack Robinson. We find that Thomas Derrick was a thoroughly bad man whose death sentence was commuted on the condition that he become the executioner for the Earl of Essex. The gallows is also called a derrick in his "honor", and the word is now applied to various kinds of lifting structures. Jack Robinson has several variously plausible sources, but the most likely is that Sir John Robinson, constable of the Tower of London, carried out executions with great efficiency, getting them over with so quickly that it was said you couldn't say "Jack Robinson" between the time you were called out and your head rolled. The final part of executions got even quicker when the mild Dr. Guillotin was placed on a commission to reform executions. Having seen a German head-chopping blade, he told his colleagues that if executions had to be done, that machine would do it best. Now even the Germans call it the guillotine.
- p 247 – The word amateur, which means lover, and why love is zero in tennis. If the gentleman who created lawn tennis had had his way, it would be distinguished from hard-court tennis by being called sphairistike, which rhymes with "very sticky". We've been spared, at least in part because tennis players didn't know enough Greek to figure out the pronunciation. But then, love? Because if you do something for love, you'll do it for nothing. I still don't like it (and the entire love-15-30-40 sequence, which makes no numeric sense, because you have to win on an advantage anyway, after winning at least 3 serves).
Now if you can't imagine how the Inky Fool gets from any of these points to the others, do just read the book. Great fun!