'same-gender' originates from the English word 'same' and the word 'gender'. 'same' originates from Old English, specifically the word 'sam(e)', where 'sam' meant 'identical' or 'together'. 'gender' originates from Old French, specifically the word 'gendre', ultimately from Latin 'genus', where 'genus' meant 'kind' or 'type'.

'gender' changed from Old French 'gendre' (borrowed into Middle English as 'gendre') and eventually became the modern English word 'gender'. 'same' comes from Old English 'sam' and developed into modern 'same'. The compound 'same-gender' is a modern English formation that became more common in the 20th century as 'gender' was widely used to refer to sex.

Initially, 'gender' meant 'kind' or 'type' (from Latin 'genus'), but over time it shifted to refer to 'sex' (male/female), and the compound now means 'of the same sex'.