The south line of Wesley Cockrell's mile square survey aligns with the line of Clarendon Drive if it extended further west from Cockrell Hill Road but it does not appear that ever did any more than now. You are correct it was originally called Jimtown Road, for Jim Bumpass who had a store where the road intersected with the Wheatland Road, which was later named Hampton. A descendant of Bumpass was once a frequent poster here. The name change to Clarendon, as I recall, was because residential developers on the eastern end wanted something more formal. I don't think anyone ever determined the source of the Clarendon name.
Enoch Horton, father of Sarah Cockrell, patented 640 acres, but it was split into two separate tracts, the larger being bounded by Wesley Cockrell on the east, but that tract was irregular in shape and did not extend a full mile south from Davis. Other surveys filled in and likely the separate ownership had some bearing on the later development of the lands at the end of Jimtown / Clarendon and the extension of the road. "Sarah" explains that her father only wanted flat land for farming so located his lands mostly below the escarpment.
If you mean Merrifield rather than Merriweather, they were early settlers but apparently not before 1848 as they did not receive a Peters Colony Grant. The elder, John Merrifield, settled on land on the southeast corner of Hampton and Jefferson, The cemetery there contains his headstone but many others were lost. His cabin, a few blocks south, survived until the 1930s. John Merrifield's daughters and granddaughters married 2nd and 3rd generation Bryan, Beeman and Hunnicutt descendants. Subsequent Merrifield generations drifted south toward Cedar Hill and many are buried in the Wheatland Cemetery.