The story
From bathy- + -sphere. A genericization from the particular bathysphere in the 1930s named Bathysphere. The name bathysphere was coined decades after the introduction of the device in the 1890s.
Etymology from Wiktionary, CC BY-SA 4.0.
bathysphere
Today it means: A spherical steel deep-diving chamber with perspex windows, in which persons are lowered to the depths by a cable to study the oceans and deep-sea life; the precursor to the bathyscaphe. Full definition →