What is the reason to choose the name let as a keyword

The keyword let was chosen because it originates from mathematical notation, where "let" is used to introduce new variables (for example, "let x = 5"). This term was adopted by several early programming languages such as Scheme and BASIC, establishing a tradition in computer science. JavaScript follows this convention by using let to declare variables with block scope, providing a modern alternative to var. The choice helps make the language more familiar to programmers coming from other languages and aligns with the mathematical practice of variable assignment.

Practical Code Example

// 'let' originated from mathematical notation: 'Let x = 10 in expression'
// In JavaScript, it explicitly signals block-scoped binding:
function calculateDiscount(price) {
  let finalPrice = price; // scoped to function
  if (price > 100) {
    let discount = 20;    // scoped strictly to this if-block
    finalPrice -= discount;
  }
  // console.log(discount); // ReferenceError: discount is not defined
  return finalPrice;
}
console.log(calculateDiscount(150)); // 130