'myth-busting' is a compound of 'myth' + 'busting'. 'Myth' originates from Greek, specifically the word 'mythos' meaning 'story' or 'tale'. 'Bust' (in the sense 'to break, expose') is English slang that developed from earlier senses of 'break'/'burst' and came to be used figuratively as 'expose' or 'discredit'.

'myth' entered English via Latin and Old French from Greek 'mythos'. The compound 'myth-busting' arose in modern English (20th century) to describe activities that debunk myths; its usage became especially widespread in public discourse and media in the late 20th and early 21st centuries (popularized in part by science-communication efforts and shows such as the TV program 'MythBusters' in the 2000s).

Initially, 'myth' referred to traditional stories or legends and 'bust' meant to break; over time the compound came to mean 'to expose or disprove a false or misleading belief' and the noun/adjective nominalized sense ('the act of debunking' / 'designed to debunk') became common.