I fell in love with this lamentation for the destruction of the Temple the moment I heard it. Love is complicated, though. And the history of this song is no exception. It appears in earlier Karaite sources – in a markedly different form. It was almost assuredly penned by a Rabbanite poet, but as far as I can tell has never appeared in any modern or even earlier printed Rabbanite siddurim. Oh – and the original poem calls for the destruction of non-Jewish Nations (as does the current version in the Karaite siddur, albeit more limited than in the original). Yikes.