What makes the world oscillate

A friend of mine has a sister who is a nurse. One day, she was switching on the standing fan in her sitting room when her nurse-sister shouted from across the room, "Or-see-late! Or-see-late!"

My friend went, "What?!"

Sister shouted, "OR-SEE-LATE!"

Friend went, "Huh?!!"

Sister went, "OR-SEE-LATE! Make the fan turn lah!"

Turns out that nurse-sister is used to seeing the word "Oscillate" on the switches of fans in the hospitals.