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I use etymology to understand concepts better.

For example, cervix comes from Latin word meaning neck.

I was checking epithelium and to my surprise it comes from Greek θηλή which means nipple.

I don't understand the reason behind this naming.

Can someone please explain it to me?

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  • I damaged the epithelium of my hand while installing that pipe nipple.
    – Hot Licks
    Nov 14, 2020 at 18:37

5 Answers 5

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Most medical terms are made up by scientists.

Yes, one can parse the word 'epithelium'

epithelium - a membranous cellular tissue that covers a free surface or lines a tube or cavity of an animal body and ...

as

New Latin, from epi- + Greek thēlē nipple

because that's how it was coined in 1703 by Frederic Ruysch in his Thesaurus Anatomicus vol 3.

Ruysch created the Latin term from the Greek epi, which means on top of, and thele, which means nipple, to describe the type of tissue he found when dissecting the lip of a cadaver.

Ruysch was writing in Modern Latin and coined it out of Greek terms. The first use of 'epithelium' in English is attested by the OED:

  1. Anatomy. A non-vascular tissue forming the outer layer of the mucous membrane in animals.

1749 D. Hartley Observ. Man i. ii. 117 The Impressions can easily penetrate the soft Epithelium.

It was coined so the only explanation of the derivation would be from Ruysch's personal choice.

The explanation of that choice is not that there is any particular resemblance of the gross anatomy of a mammary gland nipple to the structure of the tissue of the inner lip, but rather that the lip tissue, while similar to skin tissue, is not the same.

The [underlying] tissue is not skin but a different substratum covered with sensitive (nervous) papillae

So he named it not 'epi dermis' but 'epi thelia', 'thelia' (Latin papilla, English nipple) being the term already chosen for the kind of tissue seen in the lip.

text from medical dictionary explaining origin of epithelium


This now kicks the can a little further down the road. 'Epithelium' was coined by Ruysch, but what is the provenance of 'papilla' (or nipple) for the tissue underneath the surface of the lip (or cheek)? This is straightforward visual analogy as that tissue looks like a series of little nipples.

image of cross section of skin showing the papillary layer (looking like a sequence of nipples) and the reticular layer

So in the end the reason for the use of 'thele' (= nipple) for flat looking tissue is that under a cross section it looks like a whole bunch of little protuberant nipples.

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  • @JEL The date of coinage by Ruysch is repeated over and over by multiple medical dictionaries, so I think it is unlikely that someone else had precedence. That was a Latin (and Dutch) neologism, I gave OED's first attestation in English. I'm not sure what you mean by 'incontrovertible evidence' and 'counterfactual culture'. I can only declare my own good faith which means nothing, but I think I have given enough links to convince yourself of the great likelihood of this provenance.
    – Mitch
    Nov 18, 2020 at 15:01
  • There's lots of analogical naming in anatomy but it's all obscurantist neologism so guessing doesn't always work. As you notice, 'cervix' is the label for the 'neck-like' transition between the vagina and the uterus, but 'cervical' is for -anything- neck-like. It could have been called 'portal' (for doorway) but that's already been used elsewhere.
    – Mitch
    Nov 18, 2020 at 15:17
  • Epithelia did not appear until Ruysch's 1704 Thesaurus Quartum (4th vol.). A rather entertaining figure in the third (1703) vol. is cross-referenced from the text in vol. 4. The vol. 3 refs are to epithelide (ablative), scan p. 72, and explanation of the naming is on scan pp. 30-31, where the name is compounded with dixero ("I shall call"?) and appears as epithelidadixero. English 'epithelium' not evident until 1749.
    – JEL
    Nov 18, 2020 at 18:19
  • Ruysch can (and did) make whatever claims he wanted, but I think the figure with the guideline to the infant's lip says it all: the infant's lip goes upon the nipple...and that's why thele is and continues to be so popular.
    – JEL
    Nov 18, 2020 at 18:25
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http://www.brainkart.com/article/Epithelial-Tissue_33167/

The functions of epithelium includes protection, absorption, filtration, excretion, secretion and sensory reception.

[...]

Exocrine glands secrete mucus, saliva, earwax, oil, milk, digestive enzymes and other cell products. These products are released through ducts or tubes. In contrast endocrine glands do not have ducts.

epithlial cells are divided as below:

Epithelial Cell Types

If we consider

exocrine, adj.

Having external secretion; designating or pertaining to the discharge of a secretion through a duct or the secretion itself.

then we have the function of the nipple in mammals: "the discharge of a secretion through a duct"

This seems the most obvious origin at a point before the detail of the diagram above was known.

The OED records it as from the mid 18th century:

  1. Anatomy. A non-vascular tissue forming the outer layer of the mucous membrane in animals.

1749 D. Hartley Observ. Man i. ii. 117 The Impressions can easily penetrate the soft Epithelium.

I'm surprised at the lateness of this. I can only think that the (indistinguishable) Latin (epithelium) must have been used before this

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    Comprehensive. But the reasoning is very far and obscure. It's like using "shoe" to create a word related to black holes, by arguing that shoe has an opening and once leg goes in, we don't see it, thus light goes into black hole and we can't see it. Nov 14, 2020 at 18:45
  • I know my example was not a good one, but I just wanted to specify that while your reasoning is correct, it's really complicated. Nov 14, 2020 at 18:46
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    I can't help its being complicated: the way things get their names is often complicated. Compare other glands: Amygdala: Etymology: < Latin amygdala, < Greek ἀμυγδάλη almond and Pituitary: Etymology: <Latin pituita a pip
    – Greybeard
    Nov 14, 2020 at 20:23
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As mentioned by the venerable Greybeard, epithelium doesn't have much history in English. I haven't been able to discover much more history in Latin. None of the history mentions the reason the epithelium is called "upon the nipple". So I looked, and a reason is suggested by this image (epithelial cheek cells):

epithelial cheek cells

All the uses of epithelium, including those in the Latin texts, come after development of microscopes capable of showing single cells. So the name might have been suggested by the appearance of the cells as seen through a microscope. Against that theory, the fact that any single cell with a prominant nucleus would appear similar.

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TLDR: One French dictionary says that that the Latin word epithelium was first used to describe the skin that covers the nipple.

One possible answer is found in le Trésor de la langue française informatisé (The Digitized Treasury of the French Language). For épithélium, it gives the etymology:

Lat. sc. epithelium (du gr. ε ̓ π ι ́ « sur » et de θ η λ η ́ « mamelon »; le mot ayant été d'abord appliqué à la pellicule qui recouvre le mamelon du sein),

which translates as:

Scientific Latin epithelium (from the Greek ε ̓ π ι ́ “on” and from θ η λ η ́ “nipple”; the word having been first applied to the skin that covers the nipple of the breast).

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  • Was there a date on that? Ruysch could easily have 'borrowed' that use but explained it as though he came up with it himself.
    – Mitch
    Nov 18, 2020 at 15:18
  • The only date is 1832 (Raymond), which I suspect is the source that they got it from. Nov 18, 2020 at 15:21
  • However, let me note that the skin on the nipple is indeed composed of epithelial tissue, so even if Ruysch made it up, he might have coined it to describe the skin on the nipple, and then later extended it to similar tissues elsewhere in the body. Nov 18, 2020 at 15:29
  • OK. Ruysch (for Latin) was 1703, and then in English 1749 by Hartley.
    – Mitch
    Nov 18, 2020 at 15:29
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I think I may have hit upon the rather unpleasant solution.

Here is a picture of a cancer made up of squamous cells. This would have been known of in ancient Greece. It has the appearance of a nipple.

enter image description here

Looking back to a publication of 1841 we see that the epithelium is made up of squamous cells

enter image description here

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