| Definition -
A word that has been coined to echo a sound, e.g. splash and crunch.
1. The term is extremely similar, even synonymous, to the concept expressed by the phrase onomatopoeic coinage.
2. To form words imitative of sounds is to echoize. (OED s.v. echo (9))
Etymology - The word was coined c.1880 by James Murray the editor of the OED. Note that echo derives from a Greek word that means "sound."
Oxford English Dictionary - Its first citation in this sense is from 1880:
"Onomatopœia … I prefer to call echoism. [Ibid.] note, Echoism suggests the echoing of a sound heard, and has the useful derivatives echoist, echoize, and echoic.
(J. A. H. Murray Addr. Philol. Soc. 20 )