'cling' originates from Old English, specifically the word 'clingan' (also attested as 'clyngan'), where the root meant 'to fasten, adhere, or cling'.

'cling' changed from Old English 'clingan'/'clyngan' to Middle English forms such as 'clingen' or 'clengen' and eventually became the modern English word 'cling'.

Initially, it meant 'to fasten or adhere', and over time it retained that core sense while extending metaphorically to mean 'to hold on emotionally' or 'to persist in a belief'.