acus

• (Classical Latin) IPA^(key): [ˈa.kʊs]
• (modern Italianate Ecclesiastical) IPA^(key): [ˈaː.kus]

From Proto-Italic *akus, from Proto-Indo-European *h₂eḱus, from the root *h₂eḱ- (“sharp”). Related to acuō (“sharpen, whet”) and aciēs (“edge”).^[1][2]

acus f (genitive acūs); fourth declension

2. a needle, a pin
3. bodkin
4. alternative form of acus (“bran”)
   • 4 CE – c. 70 CE, Columella, De re rustica 2.14:

     nam sēmina excussa in āreā jacēbunt, superque eā paulātim eōdem modō reliquī fasciculī excutientur, ac dūrissimae quidem acūs rejectae sēparataeque erunt ā cūdentibus, minūtae vērō, quae dē siliquīs cum fabā resēderint, aliter sēcernentur.

     (please add an English translation of this quotation)

Fourth-declension noun.

From Proto-Italic *akos, from Proto-Indo-European *h₂éḱos (“tip, bristle; ear/blade of grain, awn, chaff”), from the root *h₂eḱ- (“sharp”). Cognates include agna (“ear”) and Proto-Germanic *ahaz (“ear”), Proto-Germanic *aganō, *ahanō (“chaff”) (> English awn), Ancient Greek ἄχυρον (ákhuron) (> Greek άχυρο (áchyro, “hay”)), and Tocharian B āke (“tip, peak, end”).^[1][3]

acus n (genitive aceris); third declension

2. bran, awn, chaff

   Synonym: āplūda

   • 234 BCE – 149 BCE, Cato the Elder, De agri cultura 54.2:

     sī fēnum non erit, frondem īligneam et hederāceam datō. paleās trīticeās et hordeāceās, acus fabāginum, viciam, vel dē lupīnō, item dē cēterīs frūgibus omnia condito.

     (please add an English translation of this quotation)

   • 116 BCE – 27 BCE, Marcus Terentius Varro, Agricultural Topics 1.52:

     īs trītīs oportet ē terrā subjectārī vallīs aut ventilābrīs, cum ventus spīrat lēnis. ita fit ut quod levissimum est in eō atque appellātur acus <ac palea> ēvannātur forās extrā āream ac frūmentum, quod est ponderōsum, pūrum veniat ad corbem.

     (please add an English translation of this quotation)

   • 116 BCE – 27 BCE, Marcus Terentius Varro, Agricultural Topics 1.57:

     parietēs et solum opere tēctōriō marmorātō lōrīcandī; sī minus, ex argillā mixtā acere ē frūmentō et amurcā, quod mūrem et vermem nōn patitur esse et grāna facit solidiōra ac firmiōra.

     (please add an English translation of this quotation)

   • 116 BCE – 27 BCE, Marcus Terentius Varro, Agricultural Topics 3.9.8:

     in cubīlibus, cum parturient, acus substernendum.

     (please add an English translation of this quotation)

Third-declension noun (neuter, imparisyllabic non-i-stem).

• acerātus
• acerōsus

• Ernout, Alfred, Meillet, Antoine (1985) “acus”, in Dictionnaire étymologique de la langue latine: histoire des mots (in French), 4th edition, with additions and corrections of Jacques André, Paris: Klincksieck, published 2001, page 7
• “acus”, in Charlton T. Lewis and Charles Short (1879) A Latin Dictionary, Oxford: Clarendon Press
• “acus”, in Charlton T. Lewis (1891) An Elementary Latin Dictionary, New York: Harper & Brothers
• "acus", in Charles du Fresne du Cange’s Glossarium Mediæ et Infimæ Latinitatis (augmented edition with additions by D. P. Carpenterius, Adelungius and others, edited by Léopold Favre, 1883–1887)
• acus in Gaffiot, Félix (1934) Dictionnaire illustré latin-français, Hachette.
• Carl Meißner, Henry William Auden (1894) Latin Phrase-Book‎^[1], London: Macmillan and Co.
  • you have hit the nail on the head: rem acu tetigisti
    
• “acus”, in Harry Thurston Peck, editor (1898), Harper’s Dictionary of Classical Antiquities, New York: Harper & Brothers
• “acus”, in William Smith et al., editor (1890), A Dictionary of Greek and Roman Antiquities, London: William Wayte. G. E. Marindin

From Proto-West Germanic *akusi.

acus f

1. (large) axe
   • c. 900 CE, Die altmittel- und altniederfränkischen Psalmen und Glossen [The Old Middle and Old Low Franconian psalms and glosses]:

     Also an walde holto mit acusin hiewon duri iro an that selva, an acusi in an bardon nitherwirpon sia.

     The way they hew wood with axes in the forest, so did they hew her door, and with a large and a smaller axe they knocked her down.

• barda (smaller than an acus)
• *billi, *bīal(a)

• Middle Dutch: ākes, āex
  • Dutch: aks, aaks (dated), akst (archaic, literary), akst
    • Negerhollands: aks
    • → Sranan Tongo: aksi
  • Limburgish: aaks

• “akkus”, in Oudnederlands Woordenboek, 2012