From http://web.archive.org/web/20050212060659/http://www.lewman.net/

Lewmans have been in the New World since the beginning of English
colonial settlement of New England. William Lewman in 1648 witnessed the
will of a Mr. Turnbull in Massachusetts, Anne Looman's will was probated
in 1659, Weymouth, Massachusetts. A Robert Le/o/w/man was made a freeman
in 1642, Salem, Massachusetts and may have been an ancestor. In 1735,
Captain Luman, master of a schooner owned by a Mr. Carnes of Boston, was
lost overboard off the coast of North Carolina. It was later presumed a
murder when his crew disappeared after reaching landfall. Ann Lumon of
Baltimore County, Maryland married William Pinkston in 1743. Another
line of inquiry involving what may have been some John Lewmans and
possible wives, Sarah Sprigg and Mary Driver, need documentation.

I am using the Lewman spelling for convenience at this time though all
three spellings are used. There are recorded instances of the different
spellings in the same generation. This due to tax collectors, census
takers and others spelling it as it sounded to them. If the persons
being recorded were illiterate, they couldn't very well correct the
spelling. In England, the same spelling was varied for the same reasons
during the 1500's. The name has both Anglo-Saxon and French as possible
derivations. The old English may have been Leovfman or a similar
spelling in the Domesday Book of the 11th century, meaning a person
living on a hill or high place. Lewman may have been a man living on the
Lew River in Devonshire. In the 12th century, a Count DiLumine lived in
England as part of the Norman incursion and left descendants.
Regardless, Devonshire seems to be the point of origin by the time of
the emigration to the New World and especially convenient when Plymouth
was the major port of embarkation.

Speculation can let us map out a westward route of Devonshire to
Massachusetts to Maryland, but for direct ancestral lines, we start with
Caleb Lewman in 1773 with his purchase of 220 acres of land in Frederick
County, Maryland; on a site eight miles east of Cumberland. With the
restructuring of the counties over the next twenty years, 'Lewman's
Ramble' eventually became a part of Allegany County. The land is now
Rocky Gap State Park and where the house stood is now a parking area.