He (breath) is also Brahmanaspati, for speech is Brahman (Yagur-veda), and he is her lord; therefore he is Brahmanaspati. He (breath) is also Saman (the Udgitha), for speech is Saman (Sama-veda), and that is both speech (sa) and breath (ama). This is why Saman is called Saman.

In plain words: Breath is also called Brahmanaspati, because speech is the holy word and breath rules it. Breath is also the Saman, the sung chant of the Sama Veda. The word joins "sa" (speech) and "ama" (breath), because singing needs both.