Echo (reverberation) - Echo

Japanese: エコー（反響） - えこー

…Echo comes from the name of a forest nymph in Greek mythology, originally referring to an echo. In room acoustics, this is called reverberation, and refers to reflected sound waves that have a time delay that can be distinguished from the sound waves that arrive directly from the sound source. …

From [Response]

…It is also called an echo. It is sometimes used in the same sense as reverberation, but in acoustics, it is the phenomenon in which, when a short-duration sound is made, the reflected sound is separated in time from the direct sound and can be heard once or repeatedly many times. …

From [Yamabiko]

...The phenomenon in which sound waves traveling through the atmosphere are reflected by a solid surface and return to the direction of the sound source. It is also called an echo. Generally, this refers to outdoor sound waves that are reflected by large features such as mountains, cliffs, trees, and houses. The same phenomenon that occurs indoors is called reverberation (or sometimes reverberation).

*Some of the terminology that mentions "echo" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…エコーはギリシア神話の森のニンフの名に由来し，本来は山彦のことである。室内音響では，これを反響と名付け，音源から直接に到来した音波に対し，それと聴感上区別できるような時間遅れをもつ反射音波をいう。…