Onomatopoeia means making names in Greek basically. It is the notion of producing new words to describe the objects surrounding us with our mind. But it states that the core of producing new words is merely related to phonetic expressions – for example, “thump” and “cluck” to refer to certain sounds, or how a child might call a cat a “meow-meow”. (1)
Creating new words is also about alliteration and assonance of sounds in the onomatopoeic theory. In that regard, you would probably choose a rounded sound for a rounded visual shape to yield an undulating sound for an object as a word according to the onomatopoeic theory. It would seem accurate to explain the origin of the language based on phonetic expressions but unfortunately is not. The onomatopoeic theory answers how the language might be created in the early times of our history, suggesting a logical way to comprehend the origin of the language. Nevertheless, the onomatopoeic theory does not offer a pathway as to why the rounded sounds were related to the rounded visual shapes for the human brain in the early times of our history. In other words, the onomatopoeic theory held that the link between word and sound was arbitrary and merely occurred through repeated association. To summarize, the onomatopoeic theory was discredited because it could not solve the mystery of the link between sound and visual shapes, which stimulated maybe the most significant and intricate ability – language.
(1) Ramachandran, V. S. "Phantom Limbs and Plastic Brains." The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human. New York: W.W. NORTON & COMPANY, 2012. 172. Print.
Figure - 33.1 https://steamregister.com/wp-content/uploads/2016/04/040916-language-creating-words-from-sound-630x375.jpg