emergency outpatient care; emergency department; ER
Refers to the hospital department or service providing immediate outpatient care for acute illnesses or injuries, as opposed to inpatient admission.
I went to the emergency department because I had a fever in the middle of the night.
The emergency department at this hospital is open 24 hours.
救急 means 'emergency' or 'first-aid' in general, while 救急外来 specifically refers to the outpatient emergency department.
外来 means 'outpatient' or 'ambulatory care'; 救急外来 combines this with 'emergency' to specify the emergency outpatient service.
Compound of 救急 (emergency) and 外来 (outpatient). The term is a modern medical expression with no obscure historical derivation.