before the rinderpest(In South Africa, a long time ago; referring to the 1896 epidemic of the cattle disease, treated as a landmark. // Rinderpest is a contagious viral disease of cattle that periodically caused heavy losses in much of Africa. The 1896 epidemic was so devastating that it was treated as a historical landmark, so giving rise to this expression. oxfordreference.com'More)
ages back(Technical); long long ago; way, way, way back(Lethbridge says his uncle and cousins were travelling near Cartwright in January a few years before the Black Tickle incident when they saw big swirling lights above them for a few moments before they disappeared. "People have reported unusual sightings way, way, way back, and the same as elsewhere in the world," Lethbridge said.cbc.caART Vancouver)
thesaurus.com SirReal); from the year one; years and years ago; over a long time ago (Баян); long ago; a really long time ago (VLZ_58); way back in the past (Damirules); in the days of old (Andrey Truhachev); in the days of old (Andrey Truhachev); so long ago (Побеdа); way back in the old days (4uzhoj); gazillion years ago (Raz_Sv); time out of mind; anciently