I noticed this unusual name in a book I have "The Land Records of Prince George's County, Maryland, 1717 to 1726" by Elise Greenup Jourdan:
In 1722 Stephen Yalkley is listed as a mariner, when he purchased land.
"folia 458, Indenture, 14 Apr 1723, enrolled 25 Jul 1723 - From: Stephen Yoakley of Prince George's County, Gentleman, To: Thomas Williams, planter of Prince George's County - For and in consideration of a marriage already solemnized between Stephen Yoakley and Martha Prather, formerly the wife of Thomas Prather, late of Prince George's County, dec'd, now wife of Yoakley; one moiety of a tract of land called 'Backland' in Prince George's County of 300 acres; formerly held by John Bigger and leased by Yoakley to Patrick Andrews; Martha to have use of this land for her lifetime; after her decease to Aaron Prather, son of Martha by Thomas Prather, deceased; if Aaron die before 21 to go to Rachael Prather, daughter of Martha.Signed by Stephen Yoakley (seal) Witnesses: Joseph Belt, Thomas Sprigg."
"folio 525, Deed of Gift, 25 Mar 1723; enrolled 25 Mar 1724, From: Stephen Yoakley of Prince George's County, To: John Smith Prather, Rachel Prather, Philip Prather, and Aaron Prather children of Thomas Prather late of Prince George's County - A gift of a certain sum of money due to each when they reach a certain age from the sale of the items listed below; Stephen Yoakley married Martha Prather, widow of Thomas Prather and mother of the children; Yoakley sold Thomas Williams, planter of Prince George's County, a Negro man called Hecter, one called Toby, one called Robin, one feather bed and furniture with tester, one large looking glass, four horses, one servant woman Ann Adamson and 6 slver spoons; signed Stephen Yoakley (seal); witnessed by Elines Nuthall (mark), John Baldwin Adamson."
I am not researching these people and have no further information.