Haplogroup.

"A haplogroup is defined as all the male descendants of the single person who first showed a particular mutation. These special mutations are extremely rare and identify  a group of people  over a period of tens of thousands of years. "

In simple terms, it identifies which "tribe" we belong to, which in the Orr case emerged some 10,000 years ago.

My Haplogroup, which has been tested, is Group R1a1

FTDNA say:

"The R1a1 lineage is believed to have originated in the Eurasian Steppes north of the Black  and Caspian Seas. This lineage is thought  to descend from a population of the Kurgan culture, known for the domestication of the horse ( circa 3000 BCE). These people are also believed to be the first speakers of the Indo-European language group. This lineage is found in central and western Asia, India, and in the Slavic populations of Europe. "

A lot of interesting  detail about the Kurgan Culture can be found at http://www.iras.ucalgary.ca/~volk/sylvia/Kurgans.htm

 

The evidence is that these people must have continued their migration across the Baltic Sea into Sweden and Norway . In particular their genes are reflected in the Norwegian Vikings  who were very active in the Northern Isles of Scotland, Shetland and down into the Irish Sea and along the Solway Firth where they were established for several hundred years.

The FTDNA database shows some 194 exact matches at 12 markers of which 21 have origin as Norway, 23  Germany, 23 France, 23 Ireland, 32  England , and 42 Scotland.

The Viking connection.

 

Orr Name Study Ulster Scots Reference material