Why did Isaac Newton call his version of calculus the method of fluxions?

Isaac Newton named his version of calculus the "method of fluxions" because he grounded his mathematical approach in kinematics and the concept of continuous motion.1

Newton conceptualized a variable as a "fluent," which he defined as a magnitude that flows or changes with time. He then referred to the instantaneous rate of change of that fluent as a "fluxion," a term derived from the Latin word for flowing. In his system, the fundamental objective was to investigate the relationships between these fluents and their corresponding fluxions. While his terminology was eventually superseded by the notation and differential calculus developed by G.W. Leibniz, Newton’s method remained the preferred approach among British mathematicians throughout the 18th century.21