The linguistic term, sound symbolism, refers to meaning inherent in the sound of speech, inherent in the sense of the meaning as implicit in the 'shape' of the sound, a direct linkage between sound and meaning, the sound a symbol for a meaning, exemplified trivially by the speech sound, “ow”, meaning something like, “that hurts”. The concept that some speech sounds have recognizably inherent meaning contrasts with the traditional concept of meaning attached to speech sounds through arbitrary convention.
Sound symbolism is the term for a hypothesized systematic relationship between sound and meaning. The idea that there might be a non-arbitrary relationship between the physical aspect of a speech signal and its meaning is quite an old idea, dating back at least to the time of Plato who, in his work Cratylus, had Socrates debating with two pupils the issue of whether the names for things are arbitrary or whether instead they are a natural reflection of the things named…I believe that phonetic studies -- combined with principles emerging from ethology, the science of comparative behavior -- can provide a novel basis for further informed speculation on this issue. Moreover, the principles applied to this topic can also elucidate several other controversial topics including the cause of universal patterns in intonation, the origin of certain facial expressions involving the mouth, the reason for sexual dimorphism of the vocal anatomy in humans (and other species), and whether the human vocal anatomy shows any adaptation special to speech.
The term, sound symbolism, also refers to the discipline that studies and teaches of the relationship between the sound of a vocalization and the meaning of the sound. The discipline classifies sound-symbolic relationships into a typology, and explores the nature of the different types, their relatedness, and their broader implications for linguistics and biology.