Etymology of the English word epithelium
the English word epithelium
derived from the Byzantine Greek word epi, ἐπί (upon; properly, meaning superimposition (of time, place, order, etc.), as a relation of distribution (with the genitive case); over, upon, etc.; of rest (with the dative case) at, on, etc.; of direction (with the accusative case) towards, upon, etc.)
derived from the Latin word epithelium
derived from the Greek word thele, θηλή, ϑηλή (nipple; nipple, hence middle lining layer)