I found this on ancestry.com: A name ending in –man or –er usually reflects an occupation, as in Chapman (a shopkeeper), Bowman, Dauber (a plasterer), or Turner (someone who ran a lathe).

I agree with Jonathan. In my country, a lot of surnames end with "-arachchi". In ancient times the "arachchi" was an important official in the kingdom. And though the traditions have been over for a long time, the names are still there. I think it's something common to most languages, that comes with the progression of time.

Spiderman.