Wittgenstein asks whether the application of a rule makes any sense with regard to a putative private language, one exclusive to the subject alone. How could the private individual, without any objective reference to other speakers or to a rule book or to some standard apart from his own private impressions, make any sense of getting a meaning right or getting it wrong? He argues that this makes no sense when applied to a strictly private context.
Countless eons of evolution of life — and later the evolution of the mammalian brain – came long before anything resembling a word.
As the members of the human species evolved to the next phase of their development, they became language-users. At some point in their development, humans found it useful (maybe necessary for survival) to communicate. Certain grunts, yelps, signals, etc. came to signify something: a warning, a request, a threat.