Pronotum: meaning and suffix context?

Pronotum
The pronotum (Biology) is a prominent plate-like structure that covers all or part of the thorax of some insects. The pronotum covers the dorsal surface of the thorax.

The word can be split in two parts: pro + notum.
pro is reasonably unambiguous, but the notum part is frustrating.

pro (etymonline)

1: word-forming element meaning "forward, forth, toward the front" (as in proclaim, proceed); "beforehand, in advance" (prohibit, provide);
2: The common modern sense "in favor of, on behalf of, supporting" (pro-independence, pro-fluoridation, pro-Soviet, etc.) was not in classical Latin and is attested in English from early 19c.

notus (etymologeek)

• -sḱéti Proto-Indo-European (ine-pro)
  *ǵn̥h₃sḱéti Proto-Indo-European (ine-pro) To recognise.
  (Wikipedia) *gnōskō Proto-Italic (itc-pro) Know, get to know.

It has the root *gno*, same as in "ignore"

noton (Wikipedia)

νῶτον (noton) From Proto-Indo-European *not- (“rear, buttock”);
related to Latin natis (“rump”).
a combining form meaning “the back,” used in the formation of compound words:

eg. notochord [Greek nōton, nōtos back + Latin chorda cord]
eg. notodont adj. [Gr. notos, back; odous, tooth]

What is the coinage pronotum supposed to mean? The usage and origin of notum leaves me begging for a sensible literal meaning of the word, on whether it comes from "-notus" or "-noton".

Is it supposed to be "the notable supporting structure", or "the structure preceding the back", or something else?

(Extra: there are also the genera "Lanthonotus" and "Camponotus" - do they use the same notus suffix as in pronotum?)

Janus Bahs Jacquet left a comment pointing out that νῶτον exists as an independent word in Greek (a neuter noun) with the meaning "back". See the linked LSJ entry for further details. A synonymous variant masculine form νῶτος also exists.

I think it's not really any more accurate to call -notum/-notus a suffix than it is to call -arm a suffix in the word forearm. And I think it's unnecessary to call -notum/-notus a "combining form" because it's really the same form as the independent word. A special combining form of νῶτον exists for use in words where it is not the last element of the compound: that combining form is νωτο- (noto-) (or sometimes not-, before a vowel), as in your examples of noto-chord and not-odont.

The occurrence of "Pronotum" in Burmeister's entomological texts

According to the Oxford English Dictionary (OED), pronotum was formed in German (as Pronotum) by Hermann Burmeister, first appearing in his Handbuch der Entomologie (1832) alongside the parallel formations Mesonotum and Metanotum. The OED identifies the last element as Ancient Greek νῶτον, discussed above.

Unfortunately, I haven't been able to view the German source text (if you think you'd have better luck finding the cited passage, the OED specifically cites "I. i. iii. 81" as the location in the 1832 handbook where the word Pronotum occurs).

I found an 1836 translation of Burmeister, A manual of entomology, (translated by W. E. Shuckard), that gives a etymology that doesn't seem to agree with the OED's:

The superior, which we call PRONOTUM* (Pl. IX. and XII. A,A,A, Prothorax of Kirby and Spence), takes very different figures. [...]

*This name is compounded of προ, anterior, and νότος, the back.

(p. 75)

The title page says that this translation contains "original notes and plates by the translator", so my guess is that Shuckard misspelled νῶτος as νότος in this note. Both Greek spellings would be pronounced the same way in the traditional English pronunciation of Latin and Greek (and also in modern Greek pronunciation, actually), but νότος seems to be a different word meaning "south wind". Despite the misspelling, and Shuckard's reference to the masculine rather than the neuter variant of the Ancient Greek word for "back", the meaning given by Shuckard is consistent with the OED's explanation.

Latin notus and English "notable" aren't relevant

Latin nōtus "known" is unrelated, as shown by the etymologies that you cite: PIE *ǵneh₃- is different from PIE *not-.

And "notable", from Latin nŏta, probably is unrelated to either of the preceding words. A traditional etymology connected nŏta with nōtus, but the short vowel in nŏta makes that hypothesis difficult to support: de Vaan 2008 writes that "Schrijver 1991 has clearly shown that it is impossible to derive nota from [...] *ǵneh₃- 'to know'" (Etymological Dictionary of Latin and the other Italic Languages, p. 414).

I don't see any way pronotum could represent "the notable supporting structure": it wouldn't be put together the right way (assuming you're thinking that pro- might provide the meaning "supporting" and -notum might provide the meaning "notable") and the parts don't mean that.

In a comment, someone said:

Oxford Dictionaries (now Lexico) say notum (which exists as a stand-alone word as well, without the pro-) is from Greek νῶτον referring to the back. So the notum is a plate on the back of the thorax, hence the ‘back’; the pronotum is the notum on the prothorax. – Janus Bahs Jacquet

Below is a screenshot from Google, which shows that notum is derived from nōtun and was coined in the late 19th century.

What is the coinage pronotum supposed to mean?

It helps if you understand what the pronotum is.

The insect thorax has three segments, each with a leg pair and the second and third typically with wings. The pronotum is an outgrowth of the prothorax that extends back over the meso- and metathorax.

Structures of the thorax: The thorax is the locomotive center of the insect as it contains the wings and legs. As a simplified model, the insect thorax can be thought of as a box. Under this analogy, the top of the box is the notum, the bottom is the sternum, and the sides are the pleura. Moving posteriad (front to back), the thorax is divided into three segments: the pro-, meso-, and meta- thorax. Areas of the thorax can then be designated such as the pronotum or the mesosternum

Orthoptera of the Northern Great Plains - https://www.ndsu.edu/ndmoths/hopper/anatomy.htm