The permanent tooth most commonly referred to as the "third molar" or "wisdom tooth" is indeed the third molar.

- The third molars are the last set of molars to develop and typically erupt in late adolescence or early adulthood, usually between the ages of 17 and 25.
- They are located at the very back of the mouth, behind the second molars.
- These teeth earned the name "wisdom teeth" because their appearance is associated with the age when individuals are considered to gain more maturity or "wisdom."
- Unlike the first premolars, canines, and second molars, the third molars often face issues such as impaction, misalignment, or lack of space for eruption.

Therefore, among the options provided, the correct answer is Option 2: Third molar.

Reference: Wheeler’s Dental Anatomy, Physiology and Occlusion, 10th Edition, Chapter 7: Permanent Dentition / Page 147