'content-heavy' is a modern English compound formed by combining the noun 'content' (meaning 'subject matter' or 'material') and the adjective 'heavy' (meaning 'weighty' or 'substantial') in contemporary usage to describe something rich or dense in content.

'content' comes into English via Old French 'content' and Latin roots from 'continēre' (from Latin 'com-' + 'tenēre' meaning 'to hold'), while 'heavy' comes from Old English 'hefig' (from Proto-Germanic). These separate words existed for many centuries and were combined in modern English to create the descriptive compound 'content-heavy'.

Initially, 'content' was related to the idea of being 'contained' or 'satisfied' and 'heavy' primarily meant having physical weight; over time 'content' shifted toward the sense 'subject matter' and 'heavy' acquired metaphorical senses like 'serious' or 'substantial', producing the modern meaning 'rich in content'.