'tinnie' originates from English, specifically the word 'tin' with the diminutive/adjectival suffix '-ie' (informal), where 'tin' meant 'tin' (the metal) and by extension a tin container.

'tin' (Old English 'tin') + colloquial diminutive/affectional suffix '-y/-ie' produced informal forms like 'tinny'/'tinnie' in modern English; these colloquial forms were applied to small tin containers and later to cans and small boats.

Initially, the element 'tin' referred to the metal or a small piece/container of tin; over time the colloquial 'tinnie' came to mean specifically a small tin container or can (notably a can of beer) and, regionally, a small aluminium boat.