'foobar' is a nonsense word that has multiple mythical origins. The story I favor is its use in the military as an acronym: FUBAR - Fouled Up Beyond All Recognition. The word is then commonly (mis)spelled 'foobar' somewhere later on. In Unix parlance, something that is broken is 'foobar.' The words 'foo' and 'bar' were subsequently used in illustrations of example code in the C language as a small joke. Java's roots in C syntax being what they are, the joke has carried over, although now it's only a joke to us old crusty programmers. Many people who use it now probably do so just because they've seen it before in the readings.