Jack Robinson (mythical person)

Jack Robinson is a name present in two common figures of speech. When referring to Jack Robinson, it is used to represent quickness. In contrast, the phrase "(A)round Jack Robinson's barn" has the opposite connotation, implying slowness, as it is often used to refer to circumlocution, circumvention, or doing things in roundabout or unnecessarily complicated ways.
Etymology and common variants.
Connoting quickness.
Multiple citations explain references to Jack Robinson as meaning quickness of thought or deed. The normal usage is, "(something is done) faster than you can say Jack Robinson", or otherwise, "before you can say Jack Robinson". The phrase can be traced back to the eighteenth century.
The similar phrase, "Before you can say 'Knife!'", dates from at least 1850, when it appeared in Charles Dickens' "Household Words".
In the late nineteenth century we have "Sooner than ye'll say “Jock Hector!”, He'll them describe or draw their picture." 
Connoting slowness or roundaboutness.
In contrast, the phrase "(A)round Jack Robinson's barn" has the opposite connotation, implying slowness, as it is often used to refer to circumlocution, circumvention, or doing things in roundabout or unnecessarily complicated ways. In response to an inquiry by Ken Greenwald (a forum moderator at "WordWizard"), Joan Houston Hall (Editor of the "Dictionary of American Regional English" (DARE) project at the University of Wisconsin at Madison) researched the term's etymology. Her findings are listed below, chronologically.
Hall also found numerous references to a more common variant, "Robin Hood's barn", which she noted can be found in the "Dictionary of American Regional English", Vol. 4, page 608.