'aflojar' originates from Spanish, specifically formed from the adjective 'flojo' (Old Spanish 'floxo') with the prefix 'a-' and the verbal suffix '-ar'; 'flojo' itself derives from Latin 'flaccus' meaning 'flabby' or 'loose'.

'aflojar' changed from Old Spanish forms such as 'afloxar' (with 'floxo'/'flaxo' leading to modern 'flojo') and eventually became the modern Spanish verb 'aflojar'.

Initially, it meant 'to make flaccid or loose' (related to physical looseness), but over time it evolved into broader senses including 'to loosen', 'to slacken', 'to relent', and 'to reduce intensity'.