Like other members of the Squadron Sinister, the villain Whizzer was a nod to a member of the Justice League of America—specifically Flash (Barry Allen). Unlike the rest of the Squadron Sinister, Whizzer also had a similarly named counterpart at Timely Comics (a predecessor to Marvel Comics).
Robert Frank, the original Whizzer, first appeared in USA Comics #1 (Aug. 1941). The character acquired superhuman speed and vitality from a transfusion of mongoose blood designed to save his life following a venomous snake bite. As a costumed hero, Whizzer soon became a member of the All Winners Squad, a group that also included Miss America, Sub-Mariner, Captain America (with sidekick Bucky), and the original Human Torch (with sidekick Toro).
Three decades later, Giant-Size Avengers #1 (Aug. 1974) brought Whizzer out of retirement, getting more mileage out of the character. Without the benefit of half-Atlantean physiology, or years spent in suspended animation, Whizzer had aged normally and found himself past his physical prime. For a time, indirect evidence led Whizzer to incorrectly believe that he and Miss America (now deceased) were the true parents of the mutant twins Scarlet Witch and Quicksilver.
Whizzer's own history become more complex when retroactive continuity effectively split the All Winners Squad into two new teams set during World War II. Invaders #1 (Aug. 1975) sent Sub-Mariner, Captain America, and Human Torch to battle the Axis powers in Europe. Marvel Premiere #29 (April 1976), on the other hand, placed Whizzer and Miss America, along with Red Raven and a handful of other costumed crimefighters of that era, in a homefront team called the Liberty Legion.
Perhaps to avoid confusion with the increasing prominence of the original Whizzer, the villainous Whizzer from the Squadron Sinister later changed his handle to Speed Demon. It is worth noting that, over at DC Comics, the original Flash (Jay Garrick) first appeared in Flash Comics #1 (Jan. 1940).
This image of Whizzer comes from The Official Handbook of the Marvel Universe.