'Apalachee' originates from the Muskogean-language area (likely from a Hitchiti/Apalachee form), specifically a word reported as 'apalahci' or 'apalachi', where the elements are interpreted as referring to 'people' or 'people on the other side' (a locative/ethnonymic sense).

'Apalachee' was recorded by Spanish explorers in the 16th–17th centuries as 'Apalachee' (Spanish orthography), passed into French and English usage as the tribal name, and later gave rise to related place-names (e.g., Apalachee Bay). The tribal name also influenced the name 'Appalachian' for the Appalachian Mountains through colonial transmission of the native name.

Initially it designated the specific indigenous people known to early European explorers; over time the form was applied to their language and to local place-names and regions, and it influenced other geographic names (e.g., Appalachian). Its primary modern use remains as the name of the tribe and related toponyms.