sentence structure - "How is this called" vs "What is this called"?

Which of the following is more suitable as a title for a picture with an arrow toward a part of the body's anatomy?

1. How is this called?


2. What is this called?

I need this for a picture of a part of the body, that appears without information about this part. So, I need to ask what it is called in anatomical terminology.

Answer

In American English, it's definitely "What is this called?".

"How is this called" is a common mistake with second language learners. If this phrasing is used, it will signal to any native speakers viewing the diagram that it was created by a learner.

In the Google nGram data, "How is this called" doesn't even appear.