Dear RR ji,
Parsis have surnames like Doctor,Engineer,Contractor.
I guess Screwala denotes some mechanical type of job.
But what I am surprised is Parsis are originally from Iran..what happened to their original Iranian surnames?
Even though Parsis too claim unbroken lineage some of them clearly look North Indian mixed ..some intermarriage could have taken place..they do not look 100% Iranian.
Parsis have also surnames indicating their profession like, Dorabdaruwala (dorabdaru means spices and not batli or daru), daruwala. todiwala (extractors and fermentors of liquor) etc.
Inter-marriage is the least in the case of Parsis as they are practically ex-communicated on inter-religious marriage and are not even allowed to visit their Agni temples known as (agiyAris) and the dead bodies of the deceased are not permitted to be placed at the tomb where vultures eat away the corpse. Inter-religious marriages like that of JRD Tata are exceptions.
Most are 100% Iranians of the old and their features are easily discernible. The problem is that the present Iran occupants are the invaders and have features of Arabs. So now when you compare an Irani with a Parsi, you are comparing an Arab with the native Iranian, so we get wrong impression.
Parsis have surnames associated with profession like engineer, doctor, contractor etc. and it does not take much to know that they did not have surnames originally because such professions were hardly existing then.
Most of the people identified as Parsis now are the refugees from Persia (modern day Iran) being Zorastrians escaping the persecution of Arabs. But we hardly distinguish the original set of immigrants, viz. the vedic aryans.
One has to give 100% marks to the Parsis for their total assimilation with Indian ethos and not being a trouble-creating community inspite of being native in this land for the last 1000 years (since the second influx) and more than 5000 years (the first influx).
Dasturs or the priests are the BrAhmaNas of Parsees.