The only other possible connection I have found for "DICKSON"(which is probably iffy) is Clan Chattan.

http://www.electricscotland.com/webclans/spellings.htm

All these spellings are something to consider when researching your name:

"Dick Dickason Dickeson Dickie Dickison Dickson Dicsoun Dikiesoun Dikkyson Dikson Diksonne Dikyson"

There are all kinds of reasons for different spellings; signed name differently, mis-spelled on occassion, etc...

The Scottish Tartan Museum used to have a book by an author of the last name "Black" I think, all about Scottish surnames, there origins, etc. The book is out of print and not for sale there. Worth asking Matt about.

Obviously Dickson probably means "Son of Dick", find out origin of the two names...

look into the 1890 census in Scotland, to find your grand dad and his parents. You'll need to know the city to have any luck.