Wikipedia
Dicus is one of several spellings of a surname that has also been used to represent several apparently unrelated surnames. Other most common spellings of the surname Dicus with the same pronunciation as Dicus are Dycus and Dicas.
The Dicus family in the United States is mostly descended from William and Mary Dicas, who emigrated from Chester, England, near the border of Wales, to Chestertown, on Maryland's Eastern Shore, a generation before the American Revolution. Three of their six children began the family's three major branches. John and his children moved into Pennsylvania and New York and then followed the Westward Expansion. James and his children moved across Chesapeake Bay to Baltimore and Ellicott City, Maryland, and many of their descendants remain in Maryland. Edward and his children moved to the Blue Ridge of Virginia and from there into the southern Appalachians and through the U.S. South. Dicus family etymology was a lifetime avocation of Rufus Dicus of Baltimore, who researched church records in the early to middle 1900s, and a cousin, Jacob Dicus 8th, has built on his work through extensive Internet research in recent years. The former thought the name might originally be Dutch, while the latter found a plausible Welsh derivation.