What do you call the use of deliberately outdated language in literature?

The use of deliberately outdated language in literature is referred to as archaism. This literary technique involves incorporating words and phrases from an earlier period into a work, which can evoke a sense of nostalgia, create a certain tone, or give a historical context to the text. By employing archaisms, an author can transport readers to a different era, enhancing the authenticity of the setting or the characters' voices. This is particularly effective in genres like historical fiction or poetry that aim to reflect the language of a specific time.

In contrast, neologism involves the creation of new words or phrases, rather than the use of outdated ones. Dialect refers to a particular form of language that is specific to a region or social group, focusing on contemporary language variations rather than historical ones. Jargon pertains to specialized terminology used within a particular profession or field, which does not relate to the concept of using outdated language.