I have purchased a couple of books on genealogy in Co. Donegal and "Families of Co. Donegal" to try and find more information on the origin of Glackin/Glacken.These books don't seem to have record of "Glackin" earlier than (say) 1800 in Ireland.The earliest records (muster rolls etc) from about 1600 seem to have a record of "McGlaghlin" and I initially thought that this was where Glackin came from...
But just now I have come across a website on the Doherty family (http://pw1.netcom.com/~attygene/nickname.htm) which says that Glackin was a nickname attributed to some Doherty's who lived in Inishowen (NE County Donegal).
I tried to e-mail the person who submitted this info to the website, but the e-mail bounced back so I have no other information.
I was wondering if anyone else had heard of a connection between Glackin and Doherty?(I am particularly intersted because my Glackins married Docherty/Dohertys and they are from Inishowen).