Briant and Charles Merriman were taxed in Bledsoe Countgy, Tenn. in 1815, William, Jr and Sr in Warren County, Tenn. in 1805 and 1812. William, Jr. wass born in Virginia.
The 1820 Va census index shows only six Merriman families in the entire state , two each in Caroline and Brooke counties but there were nine "Merryman" families (four were Thomas) and one "Merrymon" (Charles). Five were in Cumberland County, two including a William in New Kent County, Charles in Mecklenburg. Such often gives a clue as to where families in other states came from.
Back in ca 1740 Virginia, there was a Francis (male) Merriman in Amelia County and a William in Lancaster. Francis is recorded with both spellings, Merriman and Merryman. It probably makes no difference, same family in the early years.
In Warren/Cannon , Tenn. two Merrimans (Erwin and Philean, married Spurlocks. One couple went to Union County, Illinois.