surrogate: [17] A surrogate is etymologically someone who has been ‘asked for’ to take the place of another. The word was borrowed from Latin surrogātus, a later form of subrogātus, the past participle of subrogāre ‘nominate an alternative candidate’. This was a compound verb formed from the prefix sub-, used here in the sense ‘instead of’, and rogāre ‘ask for, propose’ (source of English interrogate, prerogative, etc). => interrogate, prerogative