'flirt' originates from English (Early Modern English/Middle English), specifically the frequentative or derivative forms like 'flirten' or early uses of 'flirt', where 'flirt' meant 'to move with a quick or sudden motion'.

'flirt' changed from Middle English/Early Modern English senses meaning 'to flick, snap, or make a sudden movement' and later acquired the sense 'to court or behave amorously in a playful way' by the 18th century, eventually becoming the modern English 'flirt'.

Initially, it meant 'a quick movement' or 'to move suddenly', but over time it evolved into its current dominant meaning of 'to behave playfully or coquettishly toward someone' (and by extension 'to toy with' as in 'flirt with danger').