Interesting word,"Facetious"....the vowels occur in the right order (aeiou) ; "Abstemious" is another example.Horrid word !
             Anyway,I don't think that oral airflow is a causal factor - I play harmonica / mouth organ a lot,and I salivate like MAD,often having to have a quick pause to swallow. I think that "Dry Mouth" is often due to "nerves", even if one is not conscious of actually feeling nervous . It happens to me,anyway. Cider helps ,luckily !