Tariff
A tariff is called an optimal tariff if it's set to maximize the welfare of the country imposing the tariff. It is a tariff derived by the intersection between the "trade indifference curve" of that country and the offer curve of another country. In this case, the welfare of the other country grows worse simultaneously, thus the policy is a kind of "beggar thy neighbor policy". If the offer curve of the other country is a line through the origin point, the original country is in the "condition of a small country", so any tariff worsens the welfare of the original country.
Excise tax in the United States
Traditionally the federal government has left property taxes and sales taxes to the states and local governments for their revenue. Tariffs or customs duties on imported goods are essentially the only property taxes imposed by the U.S. federal government. Tariffs can be set only by the federal government, not by any state or local jurisdiction. For U.S. constitutional law purposes, a customs duty or tariff is nominally in a separate category from an excise tax. Excise taxes can be (and are) set by federal, state and local jurisdictions.