From stuff I've read elsewhere, St. Mirren was apparently the first person to preach in Paisley, hence the connection with the football club and various areas of Paisley. If you want to read more, I did a bit about it on http://www.saintmirren-mad.co.uk/news/loadnews.asp?cid=TMNW&id=151183 a few months back.
Happy St. Mirren's Day everyone :-)