One wonders if there isn’t something wrong here with the expression “to lay siege to the wilderness”. We usually expect sieges to be laid against cities, towns, and encampments, but not against the wilderness. Perhaps the preposition to should be emended to in, thus “Coriantumr did lay siege in the wilderness”. Don Brugger points out that there are examples on of “laying siege to forests and mountains” (also “besieging forests and mountains”). But we note that in all these cases the area surrounded by the besiegers has to be sufficiently small, otherwise no siege is effectively possible. And actually this is what we apparently have here in Ether 14:5, where the larger passage definitely implies some kind of investiture, a surrounding of the enemy, especially since the rest of the verse indicates how the brother of Shared escaped Coriantumr’s siege of the wilderness:
Generally, the word wilderness is used in the Book of Mormon to refer to large expanses of uninhabited land, often filled with wild animals. Occasionally, specific regions of wilderness are assigned names, such as Hermounts and Bountiful:
Even so, the word wilderness has a secondary derived meaning in the Book of Mormon—namely, as a private or secret place of retreat, presumably in a wilderness region. Consider first Amulek’s reference to private places where one can pray alone:
Later on in the Book of Mormon there are numerous references to the places of retreat used by the Gaddianton robbers. The term wilderness is used to refer to these specific places:
In fact, there is a good possibility that these uses of the singular wilderness should be interpreted as plurals—that is, as ‘wildernesses’. In early modern English, words ending in s in an unstressed syllable were often not inflected with the normal -es endings (such as the plural, possessive, or third person singular present). In such cases, the inflected form was identical to the base form. (For further discussion of this possibility in the Book of Mormon text, see under Alma 34:26.)
The Book of Mormon use of wilderness to refer to a specific place of retreat in a wilderness region seems to be the meaning in Ether 14. First of all, the specific wilderness has a name, the wilderness of Akish. And from the larger passage, the wilderness area seems to be restricted in size and thus subject to being surrounded:
Apparently verses 5 and 7 refer to the wilderness of Akish, given that the adverb again is used in verse 14.
Thus the reference to laying siege to the wilderness in Ether 14:5 makes sense given the secondary meaning of wilderness as a secret place of retreat and hiding in a wilderness region. We should note that the Oxford English Dictionary lists under definition 1c a meaning of wilderness that refers to a small wilderness that can be restricted in access: ‘a piece of ground in a large garden or park, planted with trees, and laid out in an ornamental or fantastic style, often in the form of a maze or labyrinth.’ Citations with this meaning range from about 1644 up to 1885. Of course, the Book of Mormon meaning of the word here in Ether 14 does not refer to this particular kind of wilderness. But it does show that historically the English language has allowed for the meaning of wilderness to be altered to allow for the word to refer to more restricted areas.
Summary: In Ether 14 the word wilderness appears to refer to a secret place of retreat and hiding located in a wilderness region; Alma 34:26 similarly refers to such a secret place for prayer; the use of the term wilderness as a hideout occurs generally in Helaman and 3 Nephi; in some of these cases, the form wilderness appears to have the plural meaning ‘wildernesses’; this usage suggests there is no need to emend the preposition to to in in the clause “Coriantumr did lay siege to the wilderness”.