'circa' originates from Latin, specifically the word 'circa', where 'circa' meant 'around' or 'about'.

'circa' passed from Classical/Medieval Latin into Late Latin and was borrowed into Middle English with essentially the same form ('circa'), eventually becoming the modern English 'circa'.

Initially it meant 'around' or 'about', and over time this core meaning has remained largely unchanged, retaining its use to indicate approximation (especially for dates).