Function becomes meaning: the case of Nawatl 'tla-'

The Nawatl prefix tla- is one of a series of pronominal prefixes which indicate the person, number, and honorific status of a verbal object. Its basic function or meaning is to indicate a non-human object which, for one reason or another, is left unspecified. Nonspecification is useful for a number of communicative purposes, some of them opposed to each other. For instance, it can be used to mark either an insignificant object or an object which is so obvious that it does not need to be specified. It can mark an object too holy to mention, or one too gross to mention.

In an impressive series of semantic extensions, tla- has come to designate a normal object, then a normal kind of action or process, or a general or widespread object, then a general action or process, and even a general subject. With such meanings it is sometimes used with intransitive verbs which do not accept other object prefixes. It also has come to function as a postpositional object, and as a nominal possessor. In all of these morpho-semantic developments, specific cases which can be understood in more than one way are seen to play an important part, and meaning, usage and grammar clearly proceed hand-in-hand, each influencing the other.