Meaning

noun the judicial principle asserting the supremacy of federal over state legislation on the same subject

noun the right of a government to seize or appropriate something (as property)

noun the right to purchase something in advance of others

originFrom Medieval Latin praeēmptiō (“previous purchase”), from praeemō (“buy before”), from Latin prae- (“before”) + emō (“buy”).

Etymology from Wiktionary, CC BY-SA 3.0