Australians are proud to be pioneers in the use of “bonk” to mean having sex in the 1980s. And oh, boy, once we appropriated 'bonk' as a sexual term? We really appropriate “bonk” as a sexual term. Slang dictionaries give us' bonkability '(sex appeal),' bonkhole '(anus),' bonk-on '(erection) and even' bonkbuster '(for a movie with sex scenes). I guess Game of Thrones is a “bonkbuster”?).
As for why this shift from explosions to sex? One theory (which I don't think, is too clear) is that “bonk” is “knob” the other way around. An example of a bonk is when a marathon runner reaches the 20-mile mark and cannot continue because he has exhausted all of his body's fuel. Simply highlight the game you want to buy (Ecco the Dolphin, Excite Bike and Bonk's Adventure are among the best) and select Buy.