Little known outside the Orthodox Jewish world, Wednesday is the Fast of the Tenth of Tevet. The Fast commemorates the beginning of the siege of Jerusalem by the Babylonians in the year 425 BCE which ulyimately led to the destruction of the First Temple which took place on the 9th of Av, a day on which Jews also fast as a sign of mourning.

It is from this period in time that we get the source for the english word "jeremiad" since this was time of the prophet Jeremiah who prophesied doom for the Jewish people for not following the ways of G-d. Although the word jeremiad today takes on an aspect of an overwrought complaining, at the time of the original jeremiad, the speaker could not have been more correct!

For more information about this holiday, the Chabad site is always a good source.