African nation, named for the river Niger, mentioned by that name 1520s (Leo Africanus), probably an alteration (by influence of Latin niger "black") of a local Tuareg name, egereou n-igereouen, from egereou "big river, sea" + n-igereouen, plural of that word. Translated in Arabic as nahr al-anhur "river of rivers."
word-forming element in names of countries, diseases, and flowers, from Latin and Greek -ia, noun ending, in Greek especially used in forming abstract nouns (typically of feminine gender); see -a (1). The classical suffix in its usual evolution (via French -ie) comes to Modern English as -y (as in familia/family, also -logy, -graphy). Compare -cy.
In paraphernalia, Mammalia, regalia, etc. it represents Latin or Greek -a (see -a (2)), plural suffix of nouns in -ium (Latin) or -ion (Greek), with formative or euphonic -i-.
<a href="https://www.etymonline.com/word/nigeria">Etymology of nigeria by etymonline</a>
Harper, D. (n.d.). Etymology of nigeria. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/nigeria