what is the reason why electron is called as such?

Answer 1

J J Thompson discovered the Electron in 1897, by using Cathode ray experiments and deflecting the particles with crossed fields (electric and magnetic.)

The word "elektron" in Greek means amber, the yellow fossilized resin of evergreen trees, a "natural plastic material" already known to the ancient Greeks.

It was known that when amber was rubbed with dry cloth--producing what now one would call static electricity--it could attract light objects, such as bits of paper.

And Electricity was named after the elctron also.

Answer 2

The electron as a unit of charge in electrochemistry was posited by G. Johnstone Stoney in 1874, who also coined the term electron in 1894. During the late 1890s a number of physicists posited that electricity could be conceived of as being made of discrete units, which were given a variety of names, but their reality had not been confirmed in a compelling way.