Dear Sri SANGAM,
Brahmins are SAMAVEDIS, YAJURVEDIS,DWIVEDIS, THRIVEDIS, CHATHURVEDIS etc.While DWIVEDIS learn 2 VEDAS THRIVEDIS. LEARN 3 VEDAS & CHATHUR VEDIS, all 4 Vedas. WHILE GHANA PAATIGALS in tamil Nadu and KERALA learn GHANAM SHASTRIS learn SHASTRAMS.
I am not an expert in this line. With my limited knowledge I think what I have written might be correct.
Regards & Namaskaram,
P.R.RADHAKRISHNAN
Dear Shri Radhakrishnan sir,
Since you have addressed this post to me by name, I feel I ought to say my view. According to the system followed for nearly 3000 years and more in our country among the brahmins, learning vedas was a "must" for every brahmin. His own line - rik, sAma, yajus and atharva - was compulsorily to be learned completely under the gurukula system; in addition to abiding by the discipline prescribed for the student under gurukula system, the student had to complete also various self-disciplines called "vratas" to be performed during the gurukula period.
People who completed their "vEdAdhyayana" had to undergo a samskara called "samAvartana" or "snAna" in which a ceremonial bathing was the important part; the people who underwent this, were known as "snAtakas". (Those who simply memorized the vedas without understanding the meaning thereof, were ineligible for samAvartana.)
There were three types of snAtakas — vidyAsnAtakas (those students who had studied the veda/s completely but had not completed the full term of stay in the gurukula), vratasnAtakas (those who had completed the full term of stay in the gurukulam and had observed all the "vratas", and ubhayasnAtakas (those who had finished the full course of stay and had observed all the vratas and also completely studied their veda/s.
Only ubhayasnAtaka brahmins were considered eligible to teach veda/s to further students. I am not sure whether we get such ubhayasnAtakas from our vedapAThaSAlas today.
In the milieu of the olden days described above, there were brahmin students who were very intelligent and could successfully master one, two or three vedas in addition to their own (abhivAdaye) veda; such people were given the honorifics dwivedi, trivedi and chaturvedi respectively. These were held in such high respect by the brahmins that these have stuck as family surnames even today, even though the people sporting these surnames may not know even a word of any veda!!
Colloquially, these surnames have become dubey, tiwari and chaubey, in the Hindi speaking areas.
"ghanam" is one of the "vikrutis" or kinds of analysis of the vedic samhita text. Those who used to complete all these vikrutis including ghanam (the most difficult) were called "GhanapAThin" which became 'ghanapAthi' or 'ghanapAThikaL' in our day-to-day speech. "sAstri" is a degree or title and at times it is given in appreciation of expertise in areas like Harikatha, etc., also; it does not mean that the person is well-versed in the Dharmasastras. Some institutes/colleges also give the "sastri" degree for those who complete the prescribed course of study in sanskrit etc.