'orthopyroxene' originates from Greek and New Latin: it combines the prefix 'ortho-' (from Greek 'orthos' meaning 'straight' or 'correct') with 'pyroxene' (from Greek 'pyro' meaning 'fire' and 'xenos' meaning 'stranger'), the latter having passed into New Latin mineralogical usage as 'pyroxenus'.

'pyroxene' comes from Greek 'pyroxenos' and entered scientific vocabulary via New Latin; the compound term 'orthopyroxene' was coined in mineralogy to distinguish pyroxenes with orthorhombic symmetry (orthos + pyroxene) from clinopyroxenes and became standard in 19th–20th century mineral classification.

Initially the elements of the word emphasized 'pyroxene' (a mineral associated with igneous contexts) and 'ortho-' (straight/orthorhombic); over time 'orthopyroxene' evolved into a specific mineral‑group name referring to the orthorhombic members of the pyroxene series (e.g., enstatite–ferrosilite), a narrower, technical usage in modern petrology.