'curl' originates from Middle English (late 14th century), probably from Old Norse 'krulla', where 'krulla' meant 'to make a ring or curl (a ringlet)'.

'curl' changed from Middle English forms such as 'curlen'/'curlen' and eventually became the modern English word 'curl' (with adjectival/past form 'curled').

Initially, it referred especially to a ringlet of hair ('a curl'), but over time its meaning broadened to include the action 'to form into a spiral or coil' and any curved/spiral shape.