A Brief Explanation of the Trinity - Is the word
It is not found in the Bible, probably for the reason stated in no. 2. The New Testament authors were engaged in other issues, and they assumed the reality of the Trinity, which is greater than a label. Besides, the word "tauhid" or "tawhid" or "oneness" is not found in the Quran, but Muhammad preaches this doctrine in other ways.
For more information on the absence of "tawhid" in the Quran, and scroll down to the large letters in the blue font.