Where does the name Robertson come from?

Probably from Scandinavia, where people take their father's name and add son or daughter. For instance, Peterson, Jakobson, and so on.

Very possible, but it can't go unnoticed that Roberts (short for Robertson) is very prevalent in Wales which is Celtic.

Another Answer:

I would think it would be English or Scottish.

The Scots even have a Gaelic form of the name: Robasdan. They are called "Na Robasdanaich",as well as "Clann 'IcDhonnchaidh" and "Clann Donnchaidh".

The name Robertson is Scottish. I know so because my name just happens to be Robertson and that they were kicked out of Scotland. Plus my granddad has had our history checked up on and it proves that we were Scottish at one point in time.