1540s, "element or first principle of a science or art," from French rudiment (16c.) or directly from Latin rudimentum "early training, first experience, beginning, first principle," from rudis "unlearned, untrained" (see rude).
The sense of "anything in an undeveloped state" is by 1560s. Related: Rudiments.
adjective and noun word-forming element, in most cases from Latin -arius, -aria, -arium "connected with, pertaining to; the man engaged in," from PIE relational adjective suffix *-yo- "of or belonging to." The neuter of the adjectives in Latin also were often used as nouns (solarium "sundial," vivarium, honorarium, etc.). It appears in words borrowed from Latin in Middle English. In later borrowings from Latin to French, it became -aire and passed into Middle English as -arie, subsequently -ary.
<a href="https://www.etymonline.com/word/rudimentary">Etymology of rudimentary by etymonline</a>
Harper, D. (n.d.). Etymology of rudimentary. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/rudimentary