'steadiness' originates from English, specifically formed from the adjective 'steady' plus the suffix '-ness', where 'steady' meant 'firm, stable' and '-ness' forms nouns denoting a state or quality.

'steadiness' developed from Middle English forms based on 'steady' (Middle English stedi, stedy), which in turn traces back to Old English 'stædig' (or related Old English forms) meaning 'firm, steadfast'; the modern noun 'steadiness' arose by adding the productive suffix '-ness'.

Initially it meant 'the quality of being firm or stable'; over time the use broadened to include 'consistency' and 'calmness' (e.g., steadiness of performance or composure).