Harrison was my great-grandmother's maiden name. Though I haven't focused as much on it in the past year as I did previously, I am a fairly avid genealogist. My Harrison line was one of the first that got me hooked. At the time of the Civil War, my Harrison family lived in West Virginia (Virginia initially -- my great-great-great-grandfather was a delegate to the Wheeling Convention, which ultimately resulted in the formation of West Virginia); their friends and neighbors were divided, some fighting for each side.
My great-great-grandfather was too young to enlist, so he worked as a civilian clerk under his older brother, who was a Union captain. In an act of retribution for the capture of the (soldier) brother of a confederate officer, confederate soldiers captured my great-great-grandfather and imprisoned him at Andersonville under atrocious conditions. His pension file is quite interesting, in part because he was repeatedly denied a pension since he wasn't an enlisted soldier and repeatedly had to appeal through his state representatives to receive one, as they would pass a private bill granting him a pension under the then-current pension act, which would become void when a new pension act was passed. (Sadly, this process continued even after his death as my great-great-grandmother tried to collect her widow's benefits.) He eventually became a lawyer, serving as his area's justice of the peace for many years. The house he built in the late 19th century for his family is still standing and remained in the family for 75 years. I visited it last year.
Harry is not just the most common nickname for Harrison; it was also my great-grandfather's first name (in a different branch of my family). This great-grandfather was the one my grandmother says I take after. His story is also interesting, but I'll save it for another day.
Finally, John was my father-in-law's first name.