The term is usually thought to have been coined by Albert C. Outler about 1970, though there is evidence that it was used by R. Newton Flew as long ago as the 1950s, and Outler is on record as regretting having coined the phrase 'since it has been so widely misconstrued'. The term describes the four interacting sources of authority in John Wesley's theology and has become part of Methodist theological jargon, especially in America. Wesley expanded the Anglican triad of Scripture, reason and tradition by adding 'experience'. As homo unius libri Wesley maintained the primacy of Scripture, but regularly linked it with reason (as a necessary tool of understanding and interpretation) and sometimes with tradition ('Christian antiquity' together with the accumulated wisdom of Anglicanism). To these he added, more explicitly than hitherto in Anglican theology, the role of experience in confirming scriptural truth or judging between rival interpretations. R.L. Maddox has described the quadrilateral as 'a unilateral ruleof Scripture within a trilateral hermeneuticof reason, tradition, and experience'.
See also 'Experimental Religion'.
'In fact, the term's origins are unclear. Outler claimed to have invented it, apparently around 1970, but Peter Doble tells me he heard it from R. Newton Flew in Britain in the 1950s and certainly had it in personal notes dated 1958.' (B.E. Beck, Exploring Methodism's Heritage (2004) pp.148 n.2)