RIBAT is a noun derived from the tri-consonantal root R-B-T, which carries the sense of tying or binding. It is used, for instance for bandaging a wound or tying a horse to a post. From this root, a verb was derived to mean "to be stationed, postioned, or garrisoned," in reference to an army.

The noun RIBAT then acquired the meaning of "fort."

FATH is derived from the tri-consonantal root F-T-H, which carries the meaning of opening. Since the early phase of Islamic history, it also acquired the sense of penetrating a territory, as in conquest. It has always used with a positive, self-congratulatory sense, with stated or implied belief in divine assistance in the conquest. Its meaning is similar to "victory," but the setting is always that of conquest.

So RIBAT AL-FATH would literally mean the fort of conquest or fort of victory.

As you know by now, the prefix AL- is the definitive article. So AL-RIBAT would mean "the fort." Of course, in standard Arabic pronunciation, AL-RIBAT would sound more like ARRIBAT, the L acquiring the sound of the adjacent R, hence 'er ribat' in your text.

Whether RABAT really is derived from RIBAT AL-FATH or not is something I cannot vouch for.