ذويa single meaning, dryness and desiccation — the withering of a plant or branch for want … (root dhwy)

The lexicographers in chronological order, from al-Khalīl to Lane.

Al-Khalīl gives the core image: a plant withers (yadhwī) when it is deprived of adequate watering, or when heat strikes it so that it droops and weakens; he notes the dialectal variant ḏaʾā used by the people of Bīsha. Ibn Fāris reduces the root to one sense, dryness and desiccation, matching al-Khalīl exactly. Al-Jawharī, citing Ibn al-Sikkīt, fixes the standard form as ḏawiya (fatḥa, imperfect yaḏwī) meaning ḏabala 'it drooped', and reports that the kasra form ḏawiya is rejected by Ibn al-Sikkīt though Yūnus (via Abū ʿUbayda) allows it as a dialect variant; he adds the causative aḏwāhu 'the heat withered it'. Ibn Manẓūr consolidates both masdars (ḏayy and ḏuwiyy) under the same sense and adds the ḥadīth of ʿUmar using a tooth-stick that had 'ḏawā', i.e. dried out, plus a line of verse witnessing the maṣdar ḏawiyy. Lane's gloss confirms the English sense precisely: to lose moisture, to become thin and unsubstantial after having been succulent, noting again that the kasra form is a disapproved dialectal variant.

What the theorists of sound symbolism would say of these letters. Speculative by nature.

In the scheme attributed to Ibn ʿArabī's letters-in-the-Breath, ذ is assigned to animals, و to the fixing of ranks, stations and waystations, and ي to the First Heaven — a sequence one could read allegorically as a living thing (ذ) losing its proper station (و) as it falls from its vital 'heaven' (ي), which would fit the sense of withering, though this is not a reading the tradition itself draws for this root. Al-Dabbāgh's letter-meanings for the fatḥa vocalisation describe ذ as indicating the magnification of what the self has come to possess, و as the intertwined things in the human body (veins, fingers), and ي as vocative or emphatic — none of which obviously converges on 'withering'. Mainstream historical linguistics treats such letter-symbolism as at most suggestive, not explanatory, and no claim here should be taken as more than juxtaposition.

The two-letter nucleus (Ibn Fāris's own chapters) and the permutations of the letters (Ibn Jinnī).

Ibn Fāris places ذوي beside ذوب (melting) and ذوق (tasting) as chapter-neighbours sharing the biliteral ذ-و nucleus; all three concern a substance undergoing a perceptible change of state — loosening, softening, or being assessed by contact — of which withering is the driest and most negative instance. Among the six possible triliteral permutations of ذ-و-ي, only ذوي itself is attested as a lexical root; ذيو, وذي, ويذ, يذو and يوذ are all unattested. This leaves little material for Ibn Jinnī's greater derivation (al-ishtiqāq al-akbar) beyond the ذ-و nucleus itself, and any claim of shared meaning across permutations here is necessarily speculative rather than established.

Cognates in the sister languages, and whether the word was borrowed.

No confident Semitic cognate can be identified for ذوي outside Arabic. Hebrew has a root דוה/דוי (d-w-h, 'to be sick, faint, languish'), which is semantically close, but the regular sound correspondence places Proto-Semitic *ḏ (Arabic ذ) against Hebrew ז, not ד, so a direct cognate relation cannot be asserted with confidence. There is no reason to treat ذوي as a loanword; it functions as an ordinary native Arabic root with well-attested dialectal variation (ḏaʾā) already within the Arabic lexicographical tradition.