Many words in places influenced by Arabic (or other Semitic languages) take similar forms, in this case mu_a_i_d (een is plural). Arabic has a triliteral root s

Many words in places influenced by Arabic (or other Semitic languages) take similar forms, in this case mu_a_i_d (een is plural). Arabic has a triliteral root system and this form is a way of structuring a root to indicate the person who does the thing the root refers to. I don't know if Tamil was influenced by Arabic; in this case it could be an utter coincidence.