What is the etymology of the word? Klein mentions Aramaic and Syriac cognates pitgama פתגמא meaning "word, command", and writes that they are all
borrowed from Persian. Compare Old Persian pratigama, Persian *patgam, which properly mean 'that which has come to, that which has arrived'
Since Persian is an Indo-European language, I was curious if there were any cognates in English. This site and this book suggest that patgam is cognate with the Greek pthegma which means "(spoken) word", and is found in the English word apophthegm, which more commonly appears in American English as apothegm - meaning "pithy saying" - nearly an identical meaning to the modern sense of pitgam in Hebrew. (I don't have evidence that the Greek sense influenced the modern meaning, but on the other hand, I don't know why there was a change from the Biblical - and Rabbinic - meanings to the modern one).
The Online Etymology Dictionary has this etymology for apothegm:
from Greek apophthegma "terse, pointed saying," literally "something clearly spoken," from apophthengesthai "to speak one's opinion plainly," from apo- "from" + phthengesthai "to utter."
Another word on that site with a common origin is diphthong:
late 15c., from Middle French diphthongue, from Late Latin diphthongus, from Greek diphthongos "having two sounds," from di- "double" + phthongos "sound, voice," related to phthengesthai "utter, speak loudly."
We've seen the concept of diphthong on Balashon before, even though I didn't use the official term, when we discussed the origins of the letters of the Hebrew alphabet. The letter "bet" derives from the word bayit בית (house). Some locations in ancient Israel pronounced words with a diphthong - bayit, yayin, zayit and others without - bet, yen, zet. The versions without the diphthong are preserved such cases as the letter "bet" and in the semichut form.