'ideogram' originates from French, specifically the word 'idéogramme,' where 'ideo-' is from Greek 'idea' meaning 'form, idea' and '-gram' is from Greek 'gramma' meaning 'letter' or 'something written'.

'ideogram' changed from French 'idéogramme' (19th century) and was adopted into English in the mid-19th century with essentially the same sense of 'a written symbol representing an idea'.

Initially it meant 'a written character or symbol' and over time it has remained close to that sense but is often used more specifically for symbols representing ideas rather than phonetic values.