It was named after him because he is the one who first proved the existence of electromagnetic waves which was theorized by James Maxwell and was named after him as an honor.
the wavelength and frequency of light are closely related. the higher the frequency, the shorter the wavelength. because all light waves move through a vacuum at the same speed, the number of wave crests passing by a given point in one second depends on the wavelength. that number, also known as the frequency, will be larger for a short-wavelength wave than for a long-wavelength wave.
the equation that relates wavelength and frequency for electromagnetic waves is: λν=c where λ is the wavelength, ν is the frequency and c is the speed of light.