Emily Dickinson Lexicon

REIN, n. [Fr. rêne, from resne. The It. redine is evidently from the L. retina, retinaculum, Sp. rienda. If contracted from the Latin, it is from retineo, otherwise from the root of arrest.]

1. The strap of a bridle, fastened to the curb or snaffle on each side, by which the rider of a horse restrains and governs him.
2. The instrument of curbing, restraining or governing; government. – Shak. To give the reins, to give license; to leave without restraint. – Pope. To take the reins, to take the guidance or government.