What is the etymology of word thermometer?

The word "thermometer" comes from the Greek words θερμός (thermos) meaning "hot" and μέτρον (metron) meaning "measure".

Here's the breakdown:

* θερμός (thermos) -> thermo- (meaning "heat" or "hot")

* μέτρον (metron) -> -meter (meaning "measure")

Therefore, "thermometer" literally means "heat measure".