The phrase "write off" refers to the process of dismissing a debt or an asset as a loss, meaning that it is regarded as uncollectible or no longer of value. In accounting, it involves removing an asset or expense from the financial records because it is considered unlikely to be recovered. In a broader context, it can also mean to disregard someone or something as not worth consideration.
The term "write off" comes from the combination of "write," meaning to inscribe or record, and "off," which implies the removal or negation of something. The phrase has been used in accounting and financial contexts since at least the early 20th century.