Back in the 1980s when I was in high school, we had vocabulary words each week to watch for in print or on television. Irksome was one of those words. It was quite possibly the most difficult one to find as well. I think that most people use the synonyms for this word rather than irksome as it is a difficult word to say. People with speech impediments would definitely find it not easy. And I am sure the general population would find it tiresome to read as well.
Irksome is an irksome word indeed.