SCUBA is an acronym for Self-Contained Underwater Breathing Apparatus. These initials originated in 1939 in the US Navy to refer to US military diver's rebreather sets. As with radar, the acronym has become so familiar that it is often not capitalised and is treated as an ordinary word: for example, it has been taken into the Welsh language as "sgwba". A scuba set provides a scuba diver with the breathing gas necessary to breathe underwater.