REIN  , a guiding or controlling

leather strap or thong, attached to the bit of a ridden or driven horse (see SADDLERY) . The word is taken from the O . Fr. rene, modern rem, and is usually traced to a supposed Late Latin substantive retina formed from retinere, to hold back, restrain, cf. classical Latin retinaculum, halter . The word, usually in the plural, has been often used figuratively, as a type of that which guides, restrains or controls, e.g. in such phrases as the " reins of government," &c . The " reins," i.e. the kidneys (Lat. renes, cf . Gr . 4piiv, the midriff), or the place where the kidneys are situated, hence the loins, also, figuratively, the seat of the emotions or affections, must be distinguished .