'pH-triggered' is a modern English compound formed from 'pH' (the scientific abbreviation referring to acidity/basicity) and the past-participle/adjective 'triggered' (from the verb 'trigger').

'pH' was coined in the early 20th century (Sørensen, 1909) as a notation for hydrogen ion activity/acid strength; 'trigger' as a verb/noun developed in English to mean a mechanism or action that causes a response, and 'triggered' became used as an adjectival past-participle. The compound 'pH-triggered' arose in scientific/technical contexts to describe processes activated by pH changes.

Originally, 'trigger' referred to a physical part or action that causes release (e.g., of a mechanism); over time it broadened to mean 'to cause or activate' in many contexts. In 'pH-triggered', the term specifically denotes activation caused by pH change.