Turning to the Catholic Encyclopedia, it makes the following notes regard the history of the ambo:
A word of Greek origin, supposed to signify a mountain or elevation; at least Innocent III so understood it, for in his work on the Mass (III, xxxiii), after speaking of the deacon ascending the ambo to read the Gospel, he quotes the following from Isaias (40:9): "Get thee up upon a high mountain, thou that bringest good tidings to Sion: lift up thy voice with strength".
Originally there was only one ambo in a church, placed in the nave, and provided with two flights of steps; one from the east, the side towards the altar; and the other from the west. From the eastern steps the subdeacon, with his face to the altar, read the Epistles; and from the western steps the deacon, facing the people, read the Gospels. The inconvenience of having one ambo soon became manifest, and in consequence in many churches two ambones were erected.
...they were first introduced into churches during the fourth century, were in universal use by the ninth, reaching their full development and artistic beauty in the twelfth, and then gradually fell out of use, until in the fourteenth century, when they were largely superseded by pulpits. In the Ambrosian Rite (Milan) the Gospel is still read from the ambo. They were usually built of white marble, enriched with carvings, inlays of coloured marbles Cosmati and glass mosaics.
I shall leave the question of the Greek to those with expertise in that language, but certainly many of the older ambos fit with this imagery of a high elevation or mountain insofar as they are high platforms which are ascended.
While recently going through an edition of the Ordo Romanus Primus which was published with translation and commentary as part of the Library of Liturgiology and Ecclesiology for English Readers, I happened to notice a plate such as this which showed the ambo of the duomo of Ravello:
The basic form here is comparable to other historical ambones, but what I was intrigued by in particular in this instance was the imagery, and so I looked up further images of it:
The two main figurative mosaics upon the ambo depict Jonah and the whale, with the one side showing his being swallowed by the whale, and the other, his being released -- "Then some of the scribes and Pharisees answered him [Jesus], saying: Master, we would see a sign from thee. Who answering said to them: An evil and adulterous generation seeketh a sign: and a sign shall not be given it, but the sign of Jonah the prophet. For as Jonah was in the whale's belly three days and three nights: so shall the Son of man be in the heart of the earth three days and three nights." (Matt. 12:38-40)
The Christian symbol of the peacock can also be seen.
In the course of this search, I discovered the Ravello duomo also contains quite an impressive pulpit:
Also in Ravello can be found another church, that of S. Giovanni del Toro, with similarly impressive features:
I hope some of you will find these things of some interest as well.