Because Oxygen is highly flammable and used in said facilities. The cord is probably not up to the high standard required for medical facilities. And as for the cryptic language - this cord manufacturer might just deliver a major part of their production to medical facilities, and they don't care to add or remove labels.

Not rated well enough to guarantee no sparks in a more flammable environment (probably more specifically flammable gasses)?

I seriously thought they slipped a German word on an English label and mentally just skipped over it with a “what does that word even mean?” Wasn’t till I looked at it again I realized it was an English word and made even less sense.

Every sign has a history

...I might be drunk... but maybe it means don't use it to make specific parts of your body numb, like by the vibrations?