Yes Suzy,
Gaelic is a very fickle language & back then
most were probably monolingual (only gaelic spoken) as well as illiterate & no formal spellings so there is much room for misinterpretations/mispronunciations i.e. a good open mind is needed.
I have a little knowledge of gaelic language (present day) which gets me by for what I need most of the time
An example in English, the name John or a street named High Street.
In other words, I'm familiar with
certain names in Gaelic which crop up a lot although I do have to put my thinking cap on a lot too.
In your Tighnacres/Tenacres etc. it could be dialect differences with a possible mistranscription from Gaelic to English?
I can't answer your question as I have no idea where the writer of the book found their info.
It may have been the person had 10 Acres of land which was written, Joe Bloggs (Ten acres) which was only a note of his land rather than a place name which then was given the name Tighnacres?
The number 10 in Gaelic is 'deich" pronounced Jaich...'ch' NOT 'ck', same as Loch NOT Lock
All I can tell you is that spellings changed over the years to become what they are known as today just as surnames did.
I'm very surprised there's no connection with your family Jack to the one's in the link.
It's possible though (thanks to Ruskie (Rootschatter) for changing my mind on DNA tests) that you could prove or disprove this by DNA now.
Annie