'slender-footed' is a Modern English compound formed from 'slender' + 'foot' + the adjectival suffix '-ed'. 'slender' originates from Middle English, specifically the word 'slendre' (probably from Old Norse 'slendra'), where 'slendre'/'slendra' meant 'thin' or 'slim'. 'foot' originates from Old English, specifically the word 'fōt', where 'fōt' meant 'foot'. The suffix '-ed' (in 'footed') denotes 'having' or 'characterized by'.

'slender' changed from Middle English 'slendre' (with possible influence from Old Norse 'slendra') and eventually became the modern English 'slender'. 'foot' changed from Old English 'fōt' to Middle English 'fot' and then to modern English 'foot'. The compound 'slender-footed' developed in Modern English by combining these elements.

Initially, the component words meant 'thin/slim' ('slender') and 'foot' ('foot'); over time the compound came to be used specifically to describe something 'having thin or narrow feet' in modern usage.