On a lark 25 years ago, I looked up a history of English names in the Cambridge University Library in England. That history claims that Yearwood is descended from Heoroweard, a character mentioned in the Old English Epic Beowulf (Hrothgar's brother). From that name came Harwood, Yarwood, and Yearwood, according to this source. I like this mythology, personally.
The Cambridge University archives also listed one Hugh Yearwood of London as the first student of that name at Cambridge, 1597. Another Yearwood in the 1630's or 40's was listed from Barbadoes.
I didn't check student records at Oxford.
I am still looking for the source of the Macon, Georgia Yearwoods. In 1963 I learned from an old Dr. Yearwood, DDS, of Shreveport, that three brothers migrated to Louisiana after the Civil War, and one of them went on to Texas to raise cattle. Any body know anything about the Macon bunch?