'prelacy-opposing' is a compound formed from 'prelacy' and the present-participle 'opposing'. 'Prelacy' originates from Medieval Latin 'praelacia' / Late Latin related to 'praelatus' (from Latin roots 'prae-' meaning 'before' and the notion of a 'prelate' as a preferred/appointed cleric), and 'opposing' derives from Latin 'opponere' (from prefix 'ob-' meaning 'against' and 'ponere' meaning 'to place').

'prelacy' moved into English via Medieval Latin/Old French forms (e.g. Medieval Latin 'praelacia', Old French influences) and became 'prelacy' in Middle/Modern English; 'oppose' came from Latin 'opponere' to Old French/Anglo-Norman and Middle English 'opposen', producing the modern participle 'opposing'; the compound form 'prelacy-opposing' is a modern English compound built from these elements to describe opposition to prelacy.

Individually, 'prelacy' historically named the office or system of prelates and 'oppose' meant 'to set against'; combined as 'prelacy-opposing', the compound specifically denotes being against the institution or authority of prelates in church governance.