From The Art and Popular Culture Encyclopedia
Metaphorical language is a term referring to the use of a complex system of metaphors to create a sub-language within a common language which provides the basic terms (verbs, prepositions, conjunctions) to express metaphors.
This is a common feature of religious discussion, (for example midrash or medieval Roman Catholic "common places" or modern biblespeak) wherein fluency in a religious text is often a prerequisite to participating fully in a conversation. Not just conceptual metaphors (part of every language) that express belief in analogy between generic concepts, but extremely specific metaphors involving proper names or use of concrete nouns to express generics or processes.
The Tao te ching is considered by many to be almost entirely metaphorical. For example, change is usually expressed with the “water” character, not the “change” character.
To the outsider, such terms in such combinations will likely seem esoteric or otherwise unintelligible. Only by learning the underlying patterns of events that are considered important in the religion or ethical or political system, would one be able to comprehend what was said. The religious text thus acts as a code book. Since many religious authorities believe in the self-evident truth of their doctrines, a mere exposure to the truth in the book would tend to convert outsiders trying to learn the language. However, use of such language is not confined to religious groups.