doppler

The term originates from the name of Christian Doppler, who first proposed the physical principle in 1842. This principle describes the perceived change in frequency of a wave (such as sound or light) for an observer moving relative to the wave's source. By the early 20th century, his surname was lexicalized into an adjective in scientific English to describe phenomena and instruments (e.g., Doppler radar, Doppler shift) based on this effect. Thus, a proper name evolved into a standard technical term through the process of eponymy.

The word is a proper noun eponym, derived from the surname of the Austrian physicist Christian Doppler (1803–1853). It functions as a single, unsegmentable morpheme in modern English.