The Football League was founded in 1888, 16 years after the first FA Cup competition. Since the creation of The Football League, Tottenham Hotspur is the only non-league "giant-killer" to win the Cup, taking the 1901 FA Cup with a victory over reigning league runners-up Sheffield United: although at that time, there were only two divisions and 36 clubs in the Football League, and Spurs were champions of the next lowest football tier - the Southern League and probably already good enough for the First Division (as was shown when they joined the Second Division in 1908 and immediately won promotion to the First.) Only two other actual non-League clubs have even reached the final since the founding of the League: Sheffield Wednesday in 1890 (champions of the Football Alliance, a rival league which was already effectively the Second Division, which it formally became in 1892 – Wednesday being let straight into the First Division), and Southampton in 1900 and 1902 (in which years they were also Southern League champions, proving the strength of that league: again, they were probably of equivalent standard to a First Division club at the time, but Southampton's form subsequently faded and they did not join the League till 1920 and the formation of the Third Division.)
Is there an answer to this question (If it cannot be answered, say "unanswerable"): Who won the FA Cup in 1888?
unanswerable