'backyard' originates from Old English elements: specifically 'back' (Old English 'bæc') and 'yard' (Old English 'geard'), where 'bæc' meant 'rear' and 'geard' meant 'enclosure' or 'fenced area'.

'back' (Old English 'bæc') and 'yard' (Old English 'geard') were combined in Middle English in compounds such as 'back-yerd'/'back-yarde' and eventually became the modern English compound 'backyard'.

Initially it referred simply to a 'yard or enclosed area at the back' of a dwelling; over time the basic sense has remained but usage expanded to include recreational or cultivated spaces behind houses and figurative senses (e.g., things occurring 'in one's backyard').