Our version of Tyrer used to be Theurer, which is German. It appears to have mutated to Tyrer in our family in the late 1800s in Newark, Ohio, some years after immigration. It doesn't appear to be an official name change, just a change of spelling. I found newspaper articles where they start out using Theurer, then switch to Tyrer by the end of the story. We're looking into why, but the theory so far is the pronunciation of Tyrer and Theurer were similar -- perhaps T-yur-er. It has now become "Tie-er."