How does one say "lovesick" in Latin? It's "malato d'amore" in Italian. Is it "malus amoris"? Or would that mean more "malicious love"?
Livius, Ab urbe condita 30,11 has: aeger amore:
stimulabat aegrum amore uxor socerque
Note: the person in question is madly in love with his uxor (to the degree that he follows her unwise advice), that is to say, his lawful wife. So it is not a case of lovesickness because of an unrequited love, but I would not hesitate to use the term for that as well.
This is consistent with similar uses of aeger describing an afflicted state of mind: aeger ingentibus curis (sick with enormous worries), his aeger visis (afflicted by these dreamlike visions), etc.
Georges (1910) also offers “to make someone lovesick” – aliquem morbo venereo implicare, and in case you are wondering under what circumstances you would say that, it offers: “for example, of a well.” I would strongly advise against it, however, because morbus venereus is a medical term (albeit old-fashioned) for gonorrhea (and/or syphilis).
This is just an answer inspired by d_e's very relevant comment above: "Song of Solomon 2:5 contains this exact phrase in the original Hebrew ('sick of/from love'). Vulgate translates this as amore langueo (verbal form of the expression of course)".
It is also worth pointing out that Professor Wilfried Stroh uses the very similar (adjectival) expression amore languidus in his following comment on Virgil's Eclogue X (please see this link for the source of this quote; bold mine: Mitomino):
At ego hodie id potius carmen inspiciendum puto, quod copiosissimum nobis de Galli amoribus testimonium praebet, eclogam decimam Vergilii, in qua poeta ipse pastoris personam gerit, Gallus autem in media Arcadia amore languidus longa oratione primum de Lycoride absente queritur, deinde se amoris quaedam remedia in siluis paraturum esse affirmat - frustra! desinit enim in illud celeberrimum (69): omnia vincit Amor, et nos cedamus Amori.
Latin and English both like to use "fire" imagery to speak of love, e.g. "burning with love" or "impenso animum flammavit amore" (Aeneid IV.54). "Lovesick" captures a different angle: a dejected, uncertain, or unrequited lover.
While it's not quite the same as the English phrase (for which Sebastian has provided an excellent parallel in another answer), one Latin phrase in the Aeneid captures a similar sentiment in different terms:
At pius Aeneas, quamquam lenire dolentem
solando cupit et dictis avertere curas,
multa gemens magnoque animum labefactus amore
iussa tamen divum exsequitur classemque revisit. (IV.393-6)
Literally, the bolded phrase (which describes Aeneas) means "shaken in his soul by his great love."
Shortened, "amore labefactus" seems to capture the sense of "lovesick" quite well.
In Hebrew, “to be sick,” לחלות, builds on the stem חלה/ḤôLâH (ḤLH); “sickness” -> מחלה, and “make ill” (e.g. Pr 13:12, see following quote), “becoming sick.”
“Spes quae differtur affligit [מַחֲלָה] animam…”
In the Hebraic text of SS 2:5, we have:
כִּי-חוֹלַת אַהֲבָה, אָנִי
Translating (and preserving the syntax),
“For love-sick I am [being bereft of thy Presence].”
The Latin verb langueo essentially adds up to “longing” in English, as can be better heard in the French “languir.” For example, let us compose, in the spirit of the Song of Solomon, the following phrase both in French and English:
Je languis pour le Désiré des collines éternelles. I long for the Desired one of the everlasting hills.
This is where the Latin languorem comes quite meaningfully into play, applying when one is sick and longs to recover; and/or, when one falls into sickness from longing (from “languissement”). The two ideas, sickness and longing, are therefore closely related in languorem, which also connotes the idea of desire (desiderium) used above. Whence, longing for (concupiscentia) -> desire (desiderium) -> sickness/affliction (languorem).
And thus, we can further unpack the above composition:
I long [with desire] for the Desired one of the everlasting hills [and this causes my soul to fall into sickness, since, as Pr 13:12 puts it, “hope deferred makes the heart/the soul sick.”]
And that’s where we get the proper combination of ideas to understand the use of that original Hebraic expression, חולה באהבה (to be “sick with love”/to be “love-sick”) found in the Song.
In fine, I would alternatively render amore langueo by adflictam propter amoris, both of which do semantic justice to Solomon’s חולת אהבה.
Thank you (TKR) for the comment. In this case, the original question was aiming at understanding the expression amore langueo found in the text of the Song of Solomon (SS 2:5) according to St. Jerome’s Vulgate, and asking what the Hebraic original expression behind St. Jerome’s Latin use of langueo semantically (as opposed to etymologically) entails.
Even with etymological “holes,” the French “languir” provides an interesting link which “adds up” by way of its larger hyponymy (the way lexemic entries don’t typically help one to see, as far as the strict historical derivation of words is concerned in dictionaries). The French verb “languir” takes on a semantic domain and usage larger than the primary meaning of “lack of activity,” “depletion of energy.” One “languit,” out of “languor” (= “weariness or feebleness”), including from “being sick with/debilitated by cause of [ב] love” -> amore langueo.
Whence I submit that this is in fact the case also with the biblical use of langueo, echoing some practice or usage arguably known to St. Jerome (as seen in his effort to render the Hebrew חוֹלֶה in Latin, in its specific association with the cause of such enfeeblement/languishment found, according to the Song of Songs itself, in אהבה/amore).