'pH-dependent' is a compound formed from 'pH' and 'dependent'. 'pH' was introduced by Danish chemist Søren P. L. Sørensen in 1909, derived from the German term 'potenz hydrogenii' (literally 'power of hydrogen'), and 'dependent' originates from Latin 'dependēre' (from 'de-' + 'pendēre').

'dependent' changed from the Latin verb 'dependēre' through Old French (e.g. 'dependre') and Middle English forms (e.g. 'dependen(t)') to the modern English adjective 'dependent'. The element 'pH' was coined in the early 20th century in scientific contexts and was adopted into English as the standard notation for acidity.

Initially, 'dependent' carried the sense 'to hang down' or 'to rely on', and over time it evolved to mean 'contingent on' or 'determined by'. 'pH' originally referred to the 'power of hydrogen' (a way to express hydrogen-ion activity) and has evolved into the modern quantitative measure of acidity/basicity used in chemistry and biology; together the compound now means 'whose behavior is determined by pH'.