Probably akin to pheggos and thus to phemi; to utter a clear sound, i.e. (generally) to proclaim -- speak.
see GREEK phemi
see GREEK pheggos
φθέγγεσθαι (phthengesthai) − 1 Occurrence
φθεγγόμενοι (phthengomenoi) − 1 Occurrence
φθεγξάμενον (phthenxamenon) − 1 Occurrence