TA HA. طة
The title of the xxth Surah of the Qur’an, which begins with these Arabic letters. Their meaning is uncertain. Some fancy the first letter stand for tuba, “beatitude,” and the second for Hawiyah, the name of the lowest pit of hell Tah is also, like sah, and the English “hush,” an interjection commanding silence, and might be here employed to enjoin a silent and reverential listening to the revelation to follow.
Based on Hughes, Dictionary of Islam