'fluctuating-pressure' originates from modern English, formed by combining the present-participial adjective 'fluctuating' (from the verb 'fluctuate') and the noun 'pressure'.

'fluctuate' derives from Medieval Latin 'fluctuare' (from Latin 'fluctus' meaning 'a flowing, a wave'), and 'pressure' comes from Old French 'pression' / Medieval Latin 'pressura' (from Latin 'premere' meaning 'to press'). These elements combined in modern English to form the compound 'fluctuating-pressure'.

Initially, the component words referred separately to 'to flow/oscillate' and 'force per area'; over time they combined to denote specifically 'pressure that oscillates or varies', a technical compound used in engineering and scientific contexts.