h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Nice entry, even if there is no explanation of why this interesting fact is the case (I'm guessing it's a bit difficult to explain).

My personal favourite strangely named theorem comes from the book "The Man Who Loved Only Numbers", a biography of the mathematician Paul Erdos (there should be an umlaut on the o, but I don't know how to do them in conversations on here). The problem is to do with graph theory; it was posed by one of the few female members of Erdos' 'group' of mathematicians he spoke to in his earlier days. One of the male members of the group went on to make some headway in the problem, spurred on partly by the fact he fancied the problem setter. This helped his case and one thing led to another, and the two got married four years later. Erdos hence dubbed the problem "The Happy End Problem", which I believe (from the account in the book) is a generally accepted name for it among mathematical circles.

Ruth-Aaron pairs aren't bad either (also mentioned in the same book); these are simply pairs of consecutive numbers where the sums of the prime factors of either are equal. The name comes from the Ruth-Aaron pair 714, 715 (714=2*3*7*17, 715=5*11*13; 2+3+7+17=5+11+13). 714 was Babe Ruth's record number of home runs in 1935, but this was beaten in 1974 by Hank Aaron, scoring 715. Good naming system of numerical properties, eh?