The spelling of the word "Therrien" can be explained through its IPA phonetic transcription. The first sound is the voiced dental fricative /ð/, followed by the vowel sound /ɛ/ as in "met". The next two sounds are the alveolar flaps /ɾ/ followed by the close front unrounded vowel /i/. Finally, the last two sounds are the open mid back unrounded vowel /ɛ/ as in "met" and the nasal consonant /n/. Therefore, the spelling of "Therrien" follows the phonetic sounds /ðɛɾiɛn/.
The word "Therrien" is a French surname of regional origin. Its etymology can be traced back to the region called "Thérouanne" in northern France. "Thérouanne" was a medieval town near Calais, which was the capital of the County of Artois. Over time, the name "Thérouanne" evolved and transformed into various spellings, including "Thérien", "Thériens", and eventually "Therrien". The name initially indicated someone who either originated from the town of Thérouanne or had some association with it. Today, "Therrien" is a relatively common French-Canadian surname, which can be traced back to its origins in France.