Why is SoS 8.5 ‘dē dēsertō’ not interpreted as ‘from the forsaken’?

Question

Sources and translations

Vulgate 8.5 opens with this passages:

Quæ est ista quæ ascendit dē dēsertō, dēliciīs affluēns,
 innīxa super dīlēctum suum?

This is rendered in the 2011 translation to Norwegian as:

Kven er ho som stig opp frå ørkenen,
 stødd til kjærasten?
Who is she who rises up from the desert,
 leaning on to [her] lover?

Liebeschuetz and Hill (2005: 397) render the phrase in question as:

Let us also believe, as others have it, that he has ascended from the desert, that is to say from this arid and untilled place to that region of flowering delights, where united with his brother he enjoys the pleasure of eternal life.
[Italicisation in original.]

From the original Latin:

Crēdāmus et sīcut aliī habeat, quia ascendit ā dēsertō, […]

I, however, ended up translating it as such:

Who is she who ascends from this forsaken [place], overflowing with pleasure,
 leaning on her beloved?

Dictionary entries

All dictionary entries seem to agree that the masculine participle means something abandoned, deserted or forsaken, and that to mean the literal desert, one needed the substantivised neuter which apparently only existed in the plural.

Cassell’s Latin Dictionary

dēsertus -a -um, p[articipial] adj[jective], with compar. and superl. (desero), forsaken, abandoned, deserted; locus, regio, Cic.: loca, Caes.; deserta siti regio, Sall. Subst., dēserta -ōrum, n. deserts, wildernesses, verg.

Latinsk ordbok

dēserō […] -sertus, ᴀᴅᴊ. ᴘ. ᴛʀ. ɢʀ. forlatt, ubebodd, øde; locus; solitudo d-sima; vicus; arbores (enslige, enkeltstående), [S.] P[ro]p[er]t[ius] -serta, -ōrum, ɴ. ᴘʟ. ørken, ødemark; Libyae, ferarum, [P.] V[ergilius Maro].
dēserō […] -sertus, ᴀᴅᴊ. ᴘ. ᴛʀ. ɢʀ. abandoned, uninhabited, desolate; locus; solitudo d-sima; vicus; arbores (single, isolated/detached), [S.] P[ro]p[er]t[ius] -serta, -ōrum, ɴ. ᴘʟ. desert, wilderness; Libyae, ferarum, [P.] V[ergilius Maro].

Lewis and Short

dēsertus , a, um, Part. and P. a., from desero.

dē-sĕro , rŭi, rtum, 3, v. a. Lit., I.to undo or sever one's connection with another; hence, with esp. reference to the latter, to leave, forsake, abandon, desert, give up (cf. derelinquere; more restricted in signif. than relinquere, which denotes, in general, to depart from, to leave any one. Deserere, orig. in milit. lang., implies a cowardly running away; frequently used with prodere; also in the flg. phrase: deserere vitam; and later, absol. in the sense of to desert, etc.; cf. also: linquere, destituere, deficere, discedere—freq. and class.).
I. Lit. […] B. Absol., in milit. lang., to desert, […]
II. Trop. […] B. Since the Aug. per. subst.: dēserta , ōrum, n., desert places, deserts, wastes,

Question

All dictionaries I have checked seem to agree that to indicate desert as a place, it should be neuter plural; I would have expected the Latin to be dē dēsertīs, not dē dēsertō. I understand L&H to have based their rendering of the Bible verse on the Bible translation, as it is italicised. So to my understanding, it is the translations of the Bible which have chosen the literal identification of dē dēsertō to mean from the desert, rather than allowing for a figurative translation which we can get from from the deserted place, from the desolate place or even more so from from the forsaken place. (I chose to add this in my translation, as it flowed better in English.)

Why do all of these translations choose the literal and seemingly wrong (or imprecise) from the desert rather than the figurative from the deserted, abandoned, desolate as translation of dē dēsertō?

Literature

• Ambrosius, Aurēlius: Dē Obitū Valentīniānī Cōnsōlātiō.
• Bibelen, Høgsongen kapittel 8.
• Johanssen, Jan & Nygaard, Marius & Schreiner, Emil: Latinsk ordbok, fourth revised edition by Egil Kraggerud and Bjørg Tosterud, Cappelen, Oslo 1998.
• Liebeschuetz, John Hugo Wolfgang Gideon; Hill, Carole; Ambrŏsius, Aurēlius: Ambrose of Milan, Translated Texts for Historians 43, Liverpool University Press, Liverpool, 2005.
• Lewis, Charlton T. and Short, Charles: A Latin Dictionary
• Marchant, J. R. V., M. A. & Charles, Joseph F., B. A.: Cassell’s Latin Dictionary : Latin–English and English–Latin, 24th edition revised by Marchant and Charles, Cassell and Company, London, Toronto and Melbourne, February 1946.
• Vulgata, Song of Songs chapter 8.

Answer 1

All dictionaries I have checked seem to agree that to indicate desert as a place, it should be neuter plural; I would have expected the Latin to be dē dēsertīs, not dē dēsertō.

In Classical Latin, perhaps, but you have to keep reading the full entry.

B. Since the Aug. per. subst.: dēserta , ōrum, n., desert places, deserts, wastes, Verg. E. 6, 81; id. G. 3, 342; Plin. 5, 4, 4, § 26 al.—With gen.: “Libyae deserta,” Verg. A. 1, 384; so id. G. 3, 291; Front. Strat. 1, 7, 7; Vulg. Isa. 52, 9 al.—In sing.: dēsertum , i, n. (eccl. Lat.): “in deserto,” Prud. Apoth. 774; Hier. Ep. 125, 2; Vulg. Num. 1, 1; Luc. 3, 2 et saep.

I note in particular the "eccl. Lat." part, i.e. Christian Latin, which includes the Vulgate. For what it's worth, the Latin also reflects the singular of the Hebrew הַמִּדְבָּ֔ר.