Iconicity in language is an area of study in cognitive linguistics.
In order to talk about principles of iconicity in language, we must first establish what iconicity is from a cognitive point of view and distinguish it from other conceptual pointers. An icon is a representative pointer based on similarity and resemblance. Nearly all pictures and drawings we see are icons that stand for a concept on some level. When we see a drawing of a woman, we associate that drawing with the concept of an actual woman because it looks like a woman, even though in reality it is just a bunch of two-dimensional lines and dots on a page, and no woman is actually present. The drawing is an icon because its resemblance to the real concept causes us to associate it with that concept.
Conceptual pointers that are not based on resemblance are not icons (cognitively speaking). For example the actual word "woman" also acts as a pointer to the concept of a woman in our minds, but it is not an icon. The series of letters w-o-m-a-n have no intrinsic relationship to the actual concept of a woman. They are simply agreed to point to the concept of a woman by social convention. Those outside the social convention, namely non-English speakers, would not recognize the word "woman" as pointing to the concept of a woman. Contrast this with the drawing of a woman which would be universally recognized as a woman by nearly all human beings. Thus we would say that the word "woman" is a symbol for the concept of a woman, but not an icon.
Given that all words are symbols and not icons for the most part and that language is made up of different orderings of words by another agreed upon social convention, how is it possible that language can have iconic properties? In fact it is very possible, but on a more abstract and unconscious level than with a drawing. Iconicity in language can be analyzed from many points of view, but I will discuss three here: sequential order, distance, and quantity.
Under the principle of sequential order, we tend to map the order that events occur in a sentence to the order in which they occur in real life. For example, a person might say, "I went home and did some nodding." Upon reading this sentence, we get the notion that the person went home first and then did the nodding after he got home, even though there is nothing in the sentence that explicitly indicates this. The person didn't have to say "I went home first and did some nodding after going home." Obviously, we make this assumption because the act of going home is mentioned in the sentence before the act of nodding, and we note the resemblance of this ordering to the ordering of the real life event hence this is an example of iconicity. This is a very ingrained property of our language that eliminates the need for ordering words all the time, streamlining it tremendously.
The second variation on iconicity in language is that of distance. When two objects are separated by a larger distance then they tend to have less of an impact on each other. Consider the following sentences:
I made her come back.
I asked her to come back.
I hoped that she would come back.
In the first sentence my act of "making" directly causes her act of "coming back," thus the two actions are separated by a minimum distance of words. In the second sentence, on the other hand, my act of "asking" may or may not cause her "coming back" so the two actions are further separated. While in the last sentence, my act of "hoping" has little to no direct effect on her "coming back" and thus the two are separated by the maximum distance. In general, the three types of English clause structures - sans to, with to, and with that - tend to follow this pattern in meaning, reflecting our real-life conception of distance.
Finally, the idea of iconic quantity in language is perhaps the easiest of the three to understand. In language, repetition tends to increase the degree of the concept that the speaker is trying to get across. For example, saying "a very, very good" implies a better day than just saying "a very good day." Likewise, saying "a terrible, bad day" sounds much worse than simply "a bad day" because the speaker increases the quantity of synonyms for "bad" used to describe his day. This does not have to be limited to an increase in the amount of words, for instance saying "a looong" time uses the same principle. The concept is also not limited to adjectives: "Puppies, puppies, everywhere!" In each of these cases, an increase in quantity in the language implies an increase in quantity of the concept being conveyed. We make this connection - hence iconicity.
There are many variations on the concepts outlined in this writups and this is by no means a complete examination of linguistic iconicity, which is a very broad field. However, I hope that this provides a nice introduction to the type of analysis that is possible.
My linguistics professor Dr. Todd Oakley at Case Western Reserve University
A Cognitive Exploration of Language and Linguistics by Rene Dirven and Marjolijn Verspoor