Nowadays we simply shoo pigeons away from our public gathering places. But in Vedic times, 3,000 years ago, the pigeon was a bird of ill omen, the messenger of the goddess Nirriti, a personification of misfortune, misery, and death.
There are two interpretations of the Sanskrit Janu Sirsasana, Head-to-Knee and Head-of-the-Knee. The former emphasizes the forward bend. The latter refers to the "head" of the bent knee that you use press away from you to assist the forward bend.