'stout-hearted' is a compound of 'stout' and 'hearted'. 'stout' originates from Middle English, influenced by Old French 'estout' meaning 'brave, strong', and 'hearted' comes from Old English 'heorte' (heart) with the adjectival suffix '-ed'.

'stout' developed in Middle English from Old French 'estout' (and related Germanic sources) as meaning 'strong, brave'; it combined with 'hearted' (from Old English 'heorte' → Middle English 'herte') to form the compound adjective 'stout-hearted' used in Early Modern English and later.

Initially, elements meant 'strong' or 'brave' ('stout' and 'heart' as center of feeling/courage); over time the compound preserved the sense of 'having a brave/firm heart' while 'stout' alone acquired additional senses (e.g. 'sturdy' or 'somewhat fat').