Short answers, pulled from the story.
The word colonialism originates from the Latin term colonia, which designated a type of city or outpost founded by Roman citizens under government direction. This root derives further from the Latin word for farmer and its verb form meaning to cultivate or till land.
Modern colonialism generally started when Spanish forces conquered the Canary Islands around 1492. Portuguese Prince Henry the Navigator opened sea routes after the fall of Constantinople to the Ottoman Empire in 1453.
Half the native population of Hispaniola died from smallpox in 1518 alone. Smallpox ravaged Mexico in the 1520s killing 150,000 people including the emperor in Tenochtitlan.
Jean-Paul Sartre coined the word neocolonialism in 1956 to refer to indirect forms of colonial-style exploitation. The term became popular in ex-colonies during the late 20th century.
Edward Saïd's book Orientalism published in 1978 is considered the theory's founding work though Aimé Césaire and Frantz Fanon made similar claims decades earlier. Saïd analyzed works by Balzac, Baudelaire, and Lautréamont arguing they shaped societal fantasies of European racial superiority.