According to Merriam-Webster, the word "exigency" first came into use in 1581. The noun comes from the Latin word for "demand," as it describes a situation that demands attention.
The word "exigency" can take the place of the word "crisis" or "emergency" in a sentence. For example: "The financial exigency required everyone to save money."
Some synonyms for exigency include crisis, emergency, distress, demanding situation, crunch and breaking point. Exigency can replace any phrase in a sentence describing an urgent situation that needs to be taken care of immediately.
The word "exigency" can be found in the "Military Laws of the United States" written in 1901, and in "A Treatise on the Law of Railroads" written in 1881.