This object may have specific features that others wouldn't know, in this way it is unarbitary. Language works with the issue of the arbitariness of the sign. Words strung together are used to communicate a meaning. If we had no knowledge of what 'things'mean then language wouldn't be able to communicate them. The fact that everyone has a concept of what things mean allow language to strive by universal knowledge.
Symbolism then leads to a functional advantage of acting out ,to saying words.
Mimmicking can be passed on culturally rather than biologically. One generation teaches the next to act something out. For example rabbits learn to thump the grass when something threatening like a fox endagers theirs and others' lives. Other rabbits show what this means by previous experience.