I think "multitool" isn't as widely understood, even in the US.
And to me, it's just the "irony" of using the word "army" in an analogy trying to distance from "military."
But, it turns out, it is in fact originally and still officially a Swiss Army "Soldier's Knife" (model 1890), designed by the Swiss Army, produced for them under contract, and then universally popular. The US soldiers apparently "coined the term" because they were calling it what it was, a knife made "by" the Swiss Army for their soldiers, and popular with other soldiers (specifically german officers... who called it an officer's knife) < wiki and a knife site/forum.