The spelling of the word "Thaddaios" is interesting as it contains a double "d" and double "a". The correct pronunciation can be represented using IPA phonetic transcription as /θædɑːɪɒs/. The first "d" and "a" are pronounced individually, while the second "d" and "a" create a diphthong sound. This name is believed to originate from the Aramaic language and is often associated with the Apostle Thaddaeus or Jude, one of the Twelve Apostles of Jesus.
The name "Thaddaios" is derived from the Greek name Θαδδαῖος (Thaddaios), which itself is a Hellenized form of the Aramaic name תדי (Thadai). The Aramaic name is believed to have originated from the Hebrew name תָּדַיִ (Tadday), meaning "breast" or "heart". The exact etymology and meaning of the Hebrew and Aramaic origins are not explicitly known, but it is possible that the name symbolizes strength or affection.