Here's an announcement from the Irish Family History Foundation:

We are delighted to announce the addition of 386 family surname histories to the Roots Ireland database! Written and compiled by Brian Mitchell of Derry Genealogy, these surname histories cover mostly names from the north-west of Ireland and are an invaluable guide to those researching their family histories. These family histories are free to view at no cost and with no limit to those with a current subscription.

For an introduction to the surname histories, please visit the following link:
https://www.rootsireland.ie/derry-genealogy/surname-history-introduction/ and

For a list of the surnames and surname variants click this link:
https://www.rootsireland.ie/derry-genealogy/list-of-derry-surname-histories/

To read the surname histories click this link:
https://rootsireland.ie/derry/surname-history.php