icon

\ \ [16] The etymological idea underlying icon is of ‘similarity’. It comes via Latin īcōn from Greek eikón, which was derived from a prehistoric base meaning ‘be like’. From ‘likeness, similarity’, eikón progressed semantically via ‘image’ to ‘portrait, picture’.

\ \ That was the general sense in which English acquired the word (‘The Icon, or forme of the same birde, I have caused thus to bee figured’, John Bossewell, Workes of Armorie 1572), and it was not until the early 19th century that the particular application to a ‘sacred portrait in the Eastern Orthodox church’ entered the language.