The name is also a village in Australia, where some of the Whitehead family moved to, and it’s also said to be the name of a tribe of North American indians. This could be another clue; Thomas Blackah emigrated to North America in 1857 and returned a few years later. Harald Bruff mentions that Thomas built himself a cottage down Far Side way, I believe.
The reason may not be connected with either of these.
Another view of “Koyuga” on the right of the photograph.
The building in the centre is probably the one shown just below the “A” of Koyuga on the map.
“Koyuga” in 1972
Now abandoned and partly collapsed; today there is no trace that it ever existed.