The Spanish word 'epitelial' (meaning 'epithelial') comes from combining 'epitelio' (epithelium) with the suffix '-al' (meaning 'relating to'). The word 'epitelio' itself comes from Scientific Latin 'epithelium', which was constructed from two Ancient Greek elements: 'epi-' (ἐπι-) meaning 'upon' or 'over', and 'thele' (θηλή) meaning 'nipple'. The term was originally created to describe the tissue that grows over and covers other tissues, much like how skin covers the body.

Some related Spanish words include 'epitelización' (epithelialization, the process of epithelial tissue formation) and 'epitelioide' (epithelioid, resembling epithelial tissue). While these aren't necessarily simpler, they share the same root 'epitelio' and help form a family of related medical terms in Spanish.

English speakers might recognize the related words 'epithelial', 'epithelium', and 'epithelialization', which are direct cognates of their Spanish counterparts. The prefix 'epi-' is also found in many common English words like 'epidemic' (spreading over people), 'epidermal' (over the skin), and 'epicenter' (over the center), all sharing the meaning of 'over' or 'upon' from the original Greek.