<human>:  Why is the famous mathematician Leonhard Euler called Euler?
<bot>: Leonhard Euler was born in 1707 in Basel, Switzerland. He was named after his father, who was a pastor. The name Euler is derived from the Greek word <unk>, meaning “well”. Leonhard Euler was a famous mathematician who made many important contributions to mathematics. He is best known for his work on the theory of numbers, calculus, and the calculus of variations.