Encaustic tiles are inlaid ceramic tiles and have nothing to do with encaustic painting. The term encaustic was traditionally used in two ways, to describe both encaustic painting with beeswax and a medieval enameling process.
In the nineteenth century Victorians confused inlaid ceramic tiles with tiles made using the enameling process and in error applied the term encaustic to inlaid tiles. Encaustic is now a commonly accepted name for inlaid tile work.
[source]