It's Shopska salad, not Skopska salad. The name comes from the people leaving in Sofia plains, who are called Shopi. BTW, a Shopska salad is not a true Shopska salad without fresh or roasted red peppers and ground sirene (white cheese). Feta cheese is not a good replacement for Bulgarian sirene, as it is not hard enough to grind.
I personally prefer the version with  roasted peppers and I don't put onions in the salad, as I don't like onions much. However, it could be interesting to try it with the sweet Walla Walla onions you wrote about earlier.