Strangford Lough - "Lough Cowan" in Ulster-Scots tradition?

Recently I've come across various old printed references to Strangford Lough being called "Lough Cowan", as a version of "Cuan" or "Coan". There are multiple usages of it within W.G. Lyttle's famous Ulster-Scots kailyard novel Daft Eddie and the Smugglers of Strangford Lough (a PDF of which is online here) as well as 16 references in the British Newspaper Archive, as far back as 1837.

I have re-read my copy of Daft Eddie over the past week and it's bloodthirsty stuff in places. This is slightly shocking given that it was serialised in a weekly newspaper - some say as early as 1890, but definitely in the North Down Herald and County Down Independent in summer 1905 - long before it appeared in book form. It was even serialised for radio by the BBC in Northern Ireland Home Service in July 1948 as part of Children's Hour!