Where it came from, no one knows; but in France, six hundred years ago, bribe was the alms or the food that one gave to a beggar.
When the word reached England it meant, as Chaucer used it, to steal or extort, as well as the thing stolen or extorted.
But in the sixteenth century that which was extorted was ironically regarded as a voluntary offering by the person from whom it was taken as an inducement to act in the interests of the giver. The irony thus suggested in the word bribe at that time has now been lost.
In our present use it has a sinister sound. The giver of the bribe expects or demands something in return; the taker, however reluctant, upon his acceptance agrees to the terms, whatever they may be.