saddle (n.)

Middle English sadel, from Old English sadol "contrivance secured to the back of a horse, etc., as a seat for a rider," from Proto-Germanic *sathulaz (source also of Old Norse söðull, Old Frisian sadel, Dutch zadel, zaal, German Sattel "saddle"), from PIE root *sed- (1) "to sit" + Germanic suffix *-þra, used to form neutral names of tools.

Extended to various things resembling or functioning as a saddle. Figurative phrase in the saddle "in an active position of management" is attested from 1650s. Saddle-horse "horse for riding" is from 1660s. Saddle-stitch (n.) is from bookbinding (1887).

Old English sadolian "to put a riding saddle on;" see saddle (n.). The meaning "to load with or as with a burden" is recorded by 1690s. Related: Saddled; saddling.