The term ''Brother Jonathan'' dates to The English Civil War of the 17th Century AD. It was applied to those Puritan Colonists who settled in The New England Colonies of The New World (America). ''Brother Jonathan's'' were seen to support The Parliamentarian Movement (taken from The Biblical passage in 2 Samuel) and it is also further seen in use as a derisive term by The Royalist Supporters. British Sailors used ''Brother Jonathan'' for a type to identify US Sailors (especially during The War of 1812.
In time (1790s), the term was applied to those Persons who live in New England, as ''pious and self-righteous types''. The term is said to predate the similar derisive term ''Yankee'' (as applied by those who lived in The Southern Regions of The US).
Pre-dating the iconic propaganda image known as ''Uncle Sam'', German-American Political Cartoonist Thomas Nast resurrected ''Brother Jonathan'' (briefly) in the mid-19th Century, as a means to identify The US Government and their ''high minded'' debates about American Imperialism – with regards to future territorial movements into The Caribbean and Pacific Ocean.