It's about the operations. One Does Not Simply (tm) read a dictionary. One instead performs a “lookup” for a particular item. The dictionary is designed to make this lookup fast and reliable, which matches the purpose of these data structures in software.

A dictionary maps words to their definitions. The words are the keys, the definitions are the values. Seems reasonable to me. Though as another predominantly pythoner, I do prefer map as well.

In a dictionary the value (meaning) is often (partially) implied by the key (word), by etymology etc. In the data structure there need be no relationship between the key and value other than the fact that they are a key-value pair in this instance. It introduces messy cultural concepts into what should be a clean, abstract concept.

I think dictionary is a useful high-level analogy. Small key objects mapping to potentially large, and often structured, value objects. (By structure, I mean the definition in a dictionary often includes fields like pronunciation and origin.)