Today we believe that words enable us to communicate; the word has a symbolic meaning. In ancient times, they knew a secret that words had vibratory energy contained within each sound packet.
To unlearn ordinary methods of talking with symbolic words, the Pythagorean school had initiates (students) refrain from all speech for the first five years to learn the reticence of speech, to be able to keep the schools mysteries, strengthen silence and focus on the power of each different sounds/words. Agg! Could you imagine voluntarily not speaking for five years!