In the tradition of my teachers, downward facing dog pose is called Meru asana. They learned from Swami Dr. Gitananda at the International Center for Yoga Education and Research near Pondicherry. It was explained to us that the name comes from the sacred mountain. I also found Sumeru asana (the summit pose) for downward facing dog in the book ASANA; PRANAYAMA; MUDRA; BANDHA by Swami Satyananda Saraswati.
Still loving and learning from the Q and As.
Be well,
d from Germany.