'soft-focus' is a compound formed from the English adjective 'soft' and the noun 'focus'. 'soft' comes from Old English 'sōfte' meaning 'not hard, yielding', and 'focus' was borrowed into English from Latin 'focus' meaning 'hearth; point of convergence' (later used in optics).

'soft-focus' emerged in English in the early 20th century in the context of photography and cinematography to describe lenses or techniques that produce softened images. 'focus' itself originates from Latin 'focus' and was adapted into scientific/optical usage in modern European languages before becoming part of English technical vocabulary.

Originally, 'soft' meant 'not hard' and 'focus' meant 'hearth' (Latin); over time 'focus' acquired the technical sense of a point of convergence in optics, and the compound 'soft-focus' came to mean 'intentionally softened optical image' in modern usage.