The Spanish word 'evanescencia' (meaning 'evanescence' or the quality of gradually fading away) comes from Latin roots. It starts with the Latin prefix 'e-' meaning 'out' or 'away', combined with the verb 'vanescere' meaning 'to vanish'. These combined to form the Latin verb 'evanescere' meaning 'to vanish or disappear'. The present participle form 'evanescentem' developed into the Spanish adjective 'evanescente', and finally the abstract noun suffix '-encia' was added to create 'evanescencia', referring to the quality or state of vanishing or fading away.

A simpler related Spanish word is 'evanescente', meaning 'evanescent' or 'vanishing'. This adjective form is more commonly encountered and describes something that gradually disappears or fades away. You might also encounter the verb form 'evanecerse', meaning 'to vanish' or 'to fade away'.

English speakers might recognize the connection to the word 'evanescent', which comes from the same Latin root 'evanescere'. The English noun 'evanescence' is a direct cognate of the Spanish 'evanescencia'. These words maintain very similar meanings across both languages, referring to the quality of gradually vanishing or fading away. The word gained additional recognition in English through the American rock band 'Evanescence'.