All models of the "trapdoor Springfield" were called "needle guns" due to the long firing pin and basic lack of knowledge. Probably the old-timers had heard of a "needle gun" and when they saw the trapdoors with the long firing pin, they thought of that term. In the aftermath of the Austro-Prussian war, the U.S. press had many accounts of the Prussian success, which was attributed to the "needle gun", ignoring Prussian training and the abysmal incompetence of the Austrian army and leadership.
Before someone invents a whole scenario about thousands of Prussian soldiers marching through the Old West, the U.S. never used or adopted a true needle gun. The Ordnance Department did obtain one for testing in the leadup to adopting the trapdoor, even though it was recognized as obsolete.