Is it farther or further?
1540s, from Middle French promontoire (15c.) and directly from Medieval Latin promontorium, altered (by influence of Latin mons "mount, hill") from Latin promunturium "mountain ridge, headland," probably related to prominere "jut out" (see prominent).
promontory prom·on·to·ry (prŏm'ən-tôr'ē)
A projecting part.