KDB v1 is from sometime in the late 1990’s (I met v2 in 2002; but v1 was internal use only at some investment bank).
But that follows A and A+ which were extremely column oriented and date to early 1990s or even late 1980s ; and to various APL implementations going back to the 1960’s
Columnar DBs were very much a thing among APL users (finance and operations research) but weren’t really known outside those fields - and even in those fields, there was a period of amnesia in the late ‘90s/early 2000’s
