Myths and Theories of Origin
The origin of the word Ezhava is hotly disputed. According to one theory, the etymology of the word Ezhava is 'people of Ezham', Ezham(Eelam) being an ancient Tamil name for Sri Lanka. One of the theories that is supported by the Vadakkan Paattu (Northern Ballad) of the legendary Thiyya warrior Aaromal Chekavar. Legend has it that his family were the descendants of one of the seven warriors sent to Kerala by the Sri Lankan king .
Current linguistic research indicates that the word Eelam or Eezham[thiyyar or dweepar might have derived from dweep means island again pointing srilanka.] is derived from archaic Tamil word iiZham for Toddy. As such Eezhavas most probably are an indigenous and not immigrant community.Iram or Ira in kannada also means Toddy. The community engaged in this toddy shapping are called Idigas name resembling to Ezhava. They are also called Deevaru pointing fact that they are also from a Dweep meaning island.
There is also belief that the word Eezham is old name of Srilanka and ezhavas also came from srilanka.
Ezhava is the name of a caste (religious sub-group) in the southern Indian state of Kerala. Sociologically, Ezhava caste has never found a place in the four-tier caste system of the Hindu community. Speculations of Buddhist origin and / or migration from the Sri lanka could be sought as the reasoning behind this.
Today Ezhavas make up a major community in Kerala, comprising of about 29% of its population. Until the end of Royal rule, Ezhavas were considered a backward community, because of their position outside the Hindu four-fold caste hierarchy and their unwillingness to cater to the needs of the upper caste Brahmins and royalty. Sree Narayana Guru, the greatest social reformer that Kerala has seen, was primarily responsible for the uplift of the Ezhava community.
The origin of the word Ezhava is often disputed. The most plausible explanation is that it means "people from Ezham (Sri Lanka)".
Although, traditionally agriculturists, many Ezhavas were notable as Ayurvedic physicians, warriors and traders. In fact the translation of Ashtanga Hridaya (Sanskrit Ayurvedic text) to Malayalam was done by none other than an Ezhava physician, Kayikkara Govindan Vaidyar.
Source Wikipedia: http://en.wikipedia.org/wiki/Ezhava