Greek/derivation of "isthmus"
A friend posted on FB that the origin of this world is ancient Greek for "neck of land". That makes some sense, but I have my doubts. I know some N.T. Greek, and I know that the normal word for "neck" is "trachilos". I am wondering if the actual derivation is from thúmos, from which we get the term "thymus" as in thymus gland.
the ancient Greek word ἰσθμός , transliterated as “isthmós”(cf. the English term “isthmus”) means “narrow passage” with reference to any narrow passage such as a neck of land between two seas (cf. the Isthmus of Corinth in Herodotus, The Histories, book 8, chapter 40:”… τὸν Ἰσθμὸν αὐτοὺς τειχέοντας….”) or the neck in a body , as we read in Plato, Timaeus 69 e: “….building an isthmus and boundary for the head and chest by setting between them the neck …” (….ἰσθμὸν καὶ ὅρον διοικοδομήσαντες τῆς τε κεφαλῆς καὶ τοῦ στήθους, αὐχένα μεταξὺ τιθέντες..) where ἰσθμὸν (English, isthmus) corresponds to a narrow passage which right after is called αὐχένα (accusative singular of αὐχήν, 3rd declension, meaning “neck”).
In ancient Greek, in fact, the English word “neck” corresponds to:
1. ἰσθμός (transliterated as “isthmós”, masculine noun,nominative case, 2nd declension)
2.αὐχήν (transliterated as “auchén”,masculine noun,nominative case, 3rd declension)
3.τράχηλος (transliterated as “tráchelos”, masculine noun, nominative case,2nd declension) which however indicates either the neck or the whole neck and throat.
As for the derivation of ἰσθμός (isthmós ) from θύμος , transliterated as “thúmos”(cf. thymus gland), meaning “a warty excrescence”(see Hippocrates, De alimento, 17), it is not correct, because the stem of ἰσθμός is *ἰσθ /* ἴθ connected with the verb εἶμι (éîmi, I go, whose early stem is *ei/*i) as well as with the neuter noun ἴθμα (transliterated as “íthma”, meaning “step, motion”).
On the contrary, the early stem of θύμος (“thúmos”, masculine noun, 2nd declension, meaning “ thymus gland”), probably so called because of a fancied resemblance to a bud of thyme which in ancient Greek is θύμον (i.e. thymon, neuter noun, 2nd declension) was *thu, not *ἰσθ /* ἴθ.
Lastly, as for "tráchelos “ (not “trachilos”, as you say) which in ancient Greek is τράχηλος (masculine noun, 2nd declension), it means exactly “neck”, “ throat” as well as “the whole neck and throat”, as I’ve already said.
That being stated, the origin of the English word “isthmus” is just ἰσθμός (isthmós) which means either “neck “ in a body or “neck of land” between two seas, since its stem (cf. *ἰσθ /* ἴθ connected with the verb εἶμι /éîmi, I go, whose early stem is *ei/*i , as well as with the neuter noun ἴθμα “/“íthma”, meaning “step, motion”) indicated exactly a narrow passage just as a neck of land between two seas or a neck between the head and chest in a body.
Hope this is clear enough.