The Oxford English Dictionary's definition of the word "primary":
1. Occurring or existing first in a sequence of events; belonging to the beginning or earliest stage of something; first in time....
17. In the context of academic research or writing: designating source material contemporary with the period or thing studied; designating an original document, source, or text rather than one of criticism, discussion, or summary.
"primary, adj. and n.". OED Online. December 2019. Oxford University Press. (accessed February 05, 2020).
Image originally published in Pennsylvania Journal and Weekly Advertiser. 10/31/1765. Retrieved from "Stamp Act Crisis, 1765-1766," Making the Revolution: America, 1763-1971