It is claimed that a set of 62 known (Illert, 2003) ancient Aboriginal words constitute a representative sample of the original proto-Australian lexicon whose maximum likelihood (Fisher, 1912) 'power law signature' is determined and shown to precisely fit genetically related 'modern' lexicons from south-eastern-Australia. This measure of 'sameness' builds the confidence required to justify inter-lexicon diachronic word- frequency comparisons which provide a powerful new statistical tool capable of revealing important features of ancestral grammar. This paper supplies the first ever published modern translations of authentic traditional language documented in obscure literary and archival sources which have, until recently, been lost (Dawes, 1790b; Wood, 1924; Troy, 1992) or overlooked (Everitt et al., 1900; Illert, 2001) for centuries. These newly found examples of accusative syntax supported by word- frequency data may come as quite a surprise to some linguists (Dixon, 1980; Osmond, 1989; Troy, 1992; Nichols, 1993) who, in the absence of adequate evidence, seem to have long-imagined that language from this region--if not the entire continent-- simply had to be inherently and at the core ergative. On the contrary we find that changing word-frequencies, from proto-Australian to modern times, supply overwhelming evidence of the emergence of ancient accusative prefixes which have even survived into recent centuries in the Sydney region. Additionally it is found that, over millennia, words die-off in a lexicon, replaced by others, according to the famous "mortality law' of Gompertz (1825) which also describes the likelihood of death of biological organisms within populations and is the basis for modern actuarial science (Bowers et al., 1997). Just as disease and epidemics can wipe out entire cohorts of creatures from a population, so too can syntactic change annihilate word-classes in an evolving lexicon. [ABSTRACT FROM AUTHOR]