The development and pragmatic function of a non-inference marker

That is not to say (that) is an introductory clause refuting an inference that could be drawn from the previous discourse; it often occurs in a negative context (with a positive reading) and is characteristic of written genres, with lowest frequency in fiction. The earliest examples date from the 16th century but the next examples found date from the mid- to late-19th century. The gap in the corpus data may be explained by the predominantly fiction/drama make-up of available corpora. The development of that is not to say (that) is not an entirely prototypical case of grammaticalization as certain parameters (loss of that, contracted forms) are inconclusive and there are no ‘lexical’ uses of the form and hence no ‘divergence’.