A lot vs. Alot: 9 Grammatical Pitfalls
"restriction to limited allotments," 1865, verbal noun from ration (v.). Specifically of restrictions during wartime from 1917, from conditions in England during World War I.
1550, "reasoning," later, "relation of one number to another" (1660s), then "fixed allowance of food" (1702, often rations, from French ration in this sense), from Latin rationem (nominative ratio) "a reckoning, calculation, proportion" (see ratio). The military pronunciation (rhymes with fashion) took over from the preferred civilian pronunciation (rhymes with nation) during World War I.
A regulated allocation of resources among possible users.
Note: The U.S. government has engaged in rationing usually only under conditions of extreme shortage or economic hardship; certain resources were rationed, for example, during World War II.