'detector' originates from Latin, specifically the verb 'dētegere' (also seen as 'detegere'), where the prefix 'dē-' meant 'off, away' and 'tegere' meant 'to cover'.

'detector' came into English via the verb 'detect' (from Latin 'dētegere' through Late Latin/Old French forms such as 'detectare'/'détecter') and the agentive suffix '-or', forming 'detector' in modern English.

Initially related to 'uncovering' or 'revealing' (to take away a cover), the sense shifted toward instruments or agents that locate or indicate the presence of something; the core idea of 'finding what is hidden' has been retained.