'lie-detection' originates from Modern English as a compound of 'lie' and 'detection'; 'lie' ultimately comes from Old English 'lyge', and 'detection' comes from Latin 'detectio' via Middle French/Latin, where Latin 'detegere' meant 'to uncover'.

'lie' changed from Old English 'lyge' and became the modern English 'lie'; 'detect'/'detection' evolved from Latin 'detegere' → Medieval Latin 'detectio' → Old French/Latin forms and entered English as 'detect' and 'detection', and the compound 'lie-detection' developed in Modern English to name the practice of uncovering lies.

Initially, the root 'detect' meant 'to uncover or expose'; over time the compound came to mean specifically the uncovering of falsehoods or methods for identifying lies, i.e., 'the act or study of finding lies'.