1200: the word appears with the meaning of “to rise up”
1550: first evidence of the word “upstart” meaning “beginning, start”
1590: it means (something that) “come suddenly into being”
1845: the word appears for the first time with the meaning of “action of starting up“, as the act or an instance of setting in operation or motion, and as a fledgling business enterprise.
1976: the word appears on Forbes 15 Aug. 6/2 “the … unfashionable business of investing in startups in the electronic data processing field.”
1977: on Business Week (Industr. edn) 5 Sept. “An incubator for startup companies, especially in the fast-growth, high-technology fields”
1990/2000: the word becomes highly popular thanks to the “dot.com” economy
2002: Google N-Grams, a service that measures the frequency of a word’s use within Google’s collection of scanned books shows that the usage of “startup” peaked around 2002, shortly after the burst of the “dot-com bubble”