Carabiners got their name from the use on carbine rifles of a clip with a spring loaded gate that connected the strap to the rifle. The first aluminum carabiners were made during WWII for use by military climbers (the 10th Mountain Division, Rangers, and other specially trained forces).
The first carabiner made specifically for the outdoor sport industry was made in
the U.S. by Yvon Chouinard around 1957. What made Chouninard 'biners
great was that they could support a climbers full body weight, and the
gate would still open and close. Earlier carabiners would flex enough
under load that the gate would open all the time under load. Here is a
snap link from 1897, which would have worked pretty well for climbing,
although a rack of 30 or so of these would be pretty heavy. The basic carabiner form appears much earlier in an 1868 patent.
An earlier carabiner, made for use with ropes but not for climbing, was one made in 1868 by Pelton. A form of locking carabiner was made in 1896, as shown in the patent below.