Historically, the perception that females hailing from the regions of the erstwhile Madras Presidency are shrews is based on the traditional practice of matriarchy in Malabar. It dates back at least to the Ramayana, wherein the Dravidian Woman is depicted as a 'Rakshasi' or giant black demoness & explicitly described as an 'eater of men'. This is most evident in the character of Tāṭakā, a "repulsive man-eater (puruṣādī) with a hideous face" in whom "the ugly, fearsome, & uncontrollably sexualized feminine appears at its most horrific." ('Gendered Narratives: Gender, Space & Narrative Structures in Vālmīki's Bālakāṇḍa' Sally J Sutherland Goldman. In: 'The Rāmāyana Revisited' ed. Mandakranta Bose. 47–85. New York: Oxford University Press, 2004, p 60) Likewise, Shurpanakha, Aayomukhi & Mandodari are depicted in a similar light.
In more recent times, the image of Madrasans as the combative Negresses of India has been cemented by the 'Tamil Tigress', who is epitomised by Thenmozhi Rajaratnam, the suicide bomber who assassinated Rajiv Gandhi.
2) The Angry Madrasan stereotype is also evident in the Tamil epic Silappatikaram, with its depiction of Kannagi & her all-consuming anger which destroys the entire city of Madhurai.
3) "One of the most brilliant modern examples of the Matriarchate was found in Malabar at the time of its discovery by the Portuguese in the XV century. The Nairs were found to possess a fine civilization, entirely under the control of women, at a period when woman's position in England & on the Continent of Europe, was that of a household & political slave. Of Malabar it has been said, that when the Portuguese became acquainted with the country & the people, they were not so much surprised by the opulence of their cities, the splendor of all their habits of living, the great perfection of their navy, the high state of the arts, as they were to find all this under the entire control & government of women." 'Woman, Church & State' Matilda Joslyn Gage. 2ed. NY: The Truth Seeker Co, 1893, p 22.