A suitcase nuclear device (also suitcase nuke, suitcase bomb, backpack nuke, snuke, mini-nuke, and pocket nuke) is a tactical nuclear weapon that is portable enough that it could use a suitcase as its delivery method.
H-912 transport container for Mk-54 SADM
Both the United States and the Soviet Union developed nuclear weapons small enough to be portable in specially-designed backpacks during the 1950s and 1960s.[1][2]
Neither the United States nor the Soviet Union have ever made public the existence or development of weapons small enough to fit into a normal-sized suitcase or briefcase.[3] The W48 however, does fit the criteria of small, easily disguised, and portable. Its explosive yield was extremely small for a nuclear weapon.[4][5]
In the mid-1970s, debate shifted from the possibility of developing such a device for the military to concerns over its possible use in nuclear terrorism.[6] The concept became a staple of the spy thriller genre in the later Cold War era.[7]
More: https://en.m.wikipedia.org/wiki/Suitcase_nuclear_device