Therefore Brihaspati meditated on udgîtha (Om) as that breath, and people hold it to be Brihaspati, for speech is brihatî, and he (that breath) is the lord (pati) of speech;

In plain words: The sage Brihaspati also meditated on Om as this breath. The breath is called Brihaspati because speech is called brihati, and breath is the lord (pati) of speech.