The subgenre isekai was borrowed from Japanese 異世界 (isekai), meaning “different world”, starting around 2018. The Japanese name for the genre is similarly recent, first coined in the 2010s. The genre itself is not new; it was called “trapped in another world” before its current name.

Modern isekai are strongly influenced by web serial Mushoku Tensei, which began publication in 2012. Like with Lord of the Rings, it didn’t originate of most of its genre hallmarks, but it did pull them all together into a coherent, widely-known whole. Mushoku Tensei drew a lot of influence in particular from the light novel series The Familiar of Zero (2004). Another major contributor to isekai’s current popularity is Sword Art Online, whose anime adaptation also began airing in 2012.

The isekai genre was also popular in the 1990s before falling out of favor, with notable examples including The Vision of Escaflowne (1994), Magic Knight Rayearth (1993), and Inuyasha (1996). One significant difference from modern isekai is the 1990s progenitor series were often female-led and aimed at young women.

Both parts of 異世界 were originally borrowed from Chinese perhaps a thousand years ago: 異 (yì), meaning “different”; and 世界 (sèkài), meaning “world”. 世界 first entered Chinese around 1800 years ago through Buddhist translators coming up with a gloss for Sanskrit लोकधातु (lokadhātu), meaning “world”.