The word bloke is one of the quintessential British and to a point Australian terms. Its origins are placed in the murky waters of the underworld slang of 1860s England. Here it according to Green's Dictionary of Slang, most likely derived from the Dutch world for "fool," and came to mean the "owner" or "master" of somewhere or something.
Appearing around the same time and beyond the sense of "master/owner," we see it used in the sense of "judge, prison governor, captain of a ship" thus an extension of the sense of "someone of a position of authority." It also emerges over the course of the 1840s within Australian usage, and even within the span of the 1830s and 1840s had acquired a general sense of "man", appearing in Antipodean usage during the 1850s.
The feminine form "blokess" only appears in the early 2000s within New Zealand English.
Ultimately in 1918 it also became a generic reflexive pronoun, "oneself".
This mirrors the way that many other underworld slang terms have since joined the daily vocabulary of World Englishes, whose origins tend to be either forgotten or wholly obscured due to daily usage.