What is the most common classical Latin word that we don't understand?

Question

I assume that we do not know the meaning of every single word attested in classical and older Latin (literature, inscriptions, and other material). If this assumption is false, it makes this question pointless, but a well explained justification of it would constitute a good answer.

It seems fair to assume that in general rarer words are not known as well as more common ones. Therefore many unknown words are probably hapax legomena. But are there more commonly occurring words whose meaning we don't know? In particular, what are the most common Latin words that we don't understand?

Understanding the meaning of a word is non-binary: there is a lot of room between understanding fully and knowing nothing at all. Any suggestions of poorly understood words, particularly ones occurring several times, are welcome as answers¹. Also words that have only recently been figured out are interesting. Also, the frequency of a word depends on the corpus used, but that should not invalidate the question. Instead of trying to give too stringent definitions, I trust you to make a judgement call.

Let me exclude names from this question, since their origins are often unclear and meaning (if any) is secondary to their use.

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¹ If you know a suitable word, please suggest it as an answer since it is an answer. Comments are meant for clarifying and improving the question or making related remarks, not for answers. If you can't give all the details you wanted to, perhaps someone else can help you.

Answer 1

This is a great question: it's certainly difficult to find Latin words with uncertain meaning that are not hapax legomena.

My entry is cortumio, -nis.

• L&S says that it is "an old word of the augurial language, perhaps equivalent to contumio, from contueor"
• Gaffiot’s Dictionnaire Illustré Latin-Français is more sanguine about the meaning, tracing its origin to cor and translating as "interior contemplation."
• Varro sees it as a kind of calque of cor and conspicio:

  quod cum dicunt 'conspicionem', addunt 'cortumionem', dicitur a cordis visu: cor enim cortumionis origo. (De Lingua Latina 7.9.7)

Besides Varro, who uses it about 3 times in the same discussion, this word is also seen in the Commentarii Augurum.

This is a weak entry, since it occurs only a handful of times and is likely a strange calque, but hopefully it will spark better entries!

Answer 2

I wouldn't even try to guess which words are most commonly 'not understood'.

The natural world is a rich category here, with many examples of species that cannot be exactly identified: though reasonable guesses are made, they are often with reservations. These include both plants and animals, some of which occur in several places

My off-the-cuff offering is haematopus, described by Pliny (10, 47, 64) as a red-legged bird, of which the identity can't be properly established. It seems to be either the black-winged longshanks or the oystercatcher.

Answer 3

As Tom Cotton answered, there are many possible answers in the natural world.

According to Wikipedia, both Virgil and Cicero mention aurichalc, which is famous enough to have its own Wikipedia page.

Ipse dehinc auro squalentem alboque orichalco
circumdat loricam umeris, simul aptat habendo
ensemque clipeumque et rubrae cornua cristae,
ensem, quem Dauno ignipotens deus ipse parenti
fecerat et Stygia candentem tinxerat unda.

Aeneid, book 12, line 88

Next he binds upon his shoulders a corslet stiff with gold and pale mountain bronze; withal, he fits for wear sword and shield and the horns of his ruddy crest; the sword the divine Lord of Fire had himself wrought for his father Daunus and dipped, all glowing, in the Stygian wave.
(as translated by H. Rushton Fairclough)

Wikipedia: "Orichalcum has been held to be either a gold-copper alloy, a copper-tin or copper-zinc brass, or a metal or metallic alloy no longer known."

However, this might not count as an answer to your question, since you asked specifically about Latin, and in the context of the Latin language, we know exactly what the word orichalco means. It means "whatever the Greeks meant by ὀρείχαλκος." The trouble is that we have no idea what ὀρείχαλκος meant!