'CaSO4·0.5H2O' as a notation combines chemical element and hydrate naming: 'calcium' originates from Latin 'calx' meaning 'lime'; 'sulfate' comes from 'sulfur' (Latin/Old English) plus the chemical suffix '-ate' (from New Latin usage); 'hemi-' originates from Greek 'hemi-' meaning 'half'; 'hydrate' derives from Greek 'hydor' meaning 'water'. The trade name 'plaster of Paris' originates from the gypsum quarries near Paris, France.

'calcium' was coined in modern chemistry from Latin 'calx' (lime) and adopted into chemical nomenclature; 'sulfate' developed as part of systematic chemical naming in New Latin and modern chemistry; 'hemihydrate' is a systematic descriptive formation combining Greek-derived prefix 'hemi-' + 'hydrate' developed in chemical terminology. 'Plaster of Paris' evolved from Old French and place-name usage referring to the source near Paris.

Individually, 'calcium' originally referred to lime (burnt limestone) and came to denote the element 'calcium' in modern chemistry; 'sulfate' as a suffix became the standard name for salts of sulfuric acid; 'hemihydrate' initially described a stoichiometric partial hydration ('half' a water per formula unit) and remains a technical descriptor for that hydration state. 'Plaster of Paris' originally indicated plaster sourced from Paris and is now a general trade name for calcium sulfate hemihydrate.