I am not disputing in any way the proposition that grammatically and lexically Sindarin is (both as comparative fact and in Tolkien's legendarium) related to Quenya, while Sindarin is not.
I am taking one level of phonetic similarity, namely phonematic and phonotactic compatibility.
This is testable.
A Quenya word does not have ui in last syllable, nor end it certain groups which are acceptable internally.
If th is absent from later Quenya (Third age Q), it was earlier present, so I have not counted Sindarin th as an incompatibility. Later it becomes s. All internal s in later Quenya are either earlier th or earlier ss, since earlier z becomes r. Initial z was always non-extant, but internal, no, also there in earlier quenya. Like w which later became v (a development parallell to that of Latin). So, if I have not marked any th as incompatible with Quenya in the Sindarin text, except where final, neither have I maked any w as incompatible with Quenya in the Swahili text.
Each marking of incompatibility is an underscore.
We can add making w and z for Swahili and th for Sindarin incompatible with Exile Quenya, but this I mark with italics. I also marked a morpheme non-initial f with bold in Swahili : Quenya has f, but as far as I can recall always morpheme-if-not-word-initial.
In a Sindarin word like loth or a Swahili word like zao, there will be double marking. Underscoring is for all time impossibility in position : loth, zao, Quenya never having had th or z in these positions, italics for disappearance of th and z from Quenya: loth, zao, combined thus: loth, zao. For w, this is not absolute, there is still w in nw and in cw/qu.
By incompatibility, I mean not inability of a Quenya speaker to pronounce the words, but phonetic sentiment of using a word of another language. In 18th C. at court, French oi was still pronounced as even now in Québec. "Boîte" = Sw boett, same pronunciation, and most Swedes don't know it is borrowed from French, unless they recall hearing it in school. But if one pronounces "déjà vu" correctly, in English and in Swedish the phonetic incompatibility is such one immediately knows it is a foreign word.
Tested thus, which of Sindarin and Swahili has most phonetic incompatibilities with Quenya?
I take two poems, of Sindarin I refrain from A Elbereth Gilthoniel, and turn to a more profane, though still serious text, a Sindarin translation of La belle dame sans merci, by John Keats. And of Swahili I take a poem written by an immigrant or in Denmark of African origin.
I vrennil vain ben-dihenad
Man naeg mathal, ae maethor veren,
Erui reniol ar nimp ?
I thâr pellen uin ael
Ar ú-linnar in aew .
Man naeg mathal, ae maethor veren,
I naer ar pen-lalaith ?
I dorech en-nâr pant ,
Ar tolthad en-iau coren.
Cenin loth erin hin lín,
Na naeg ar lhêw limminnen,
Ar mi nêf lín veril firiel,
I lagor pêl.
Govannen vrennil na i nain,
I bainwain, hên in-edhil,
Finnel dín and, i dâl dín lim,
Ar hin dín vrêg.
Agoren rê an ndôl dín,
Ar mêr adh rainc ar loth;
Cenn na nin sui meliel,
Ar pent na lhoss velui.
Nan roch nín meleg harn,
Ar ú-gennin nad an aur and,
An tirn na venath linnol,
in glêr edhellin.
Hirn hylch velui enni,
Ar 'lê throvan ar Viruvor,
Na ú-istassen lam e pent,
'Gen melin thenin'
Tunc nin na i fela dín,
Ar ennas nêr dín siriant,
Ar ennas sollin hin dín mrêg
mithol canad lui.
Ar tunc nan êdh nin ennas,
Ar ennas oltha enni, ae,
I ôl vedui i oltha uireb
Nan dalad amon ring.
Cennin erain thind, ar conin nimp,
ar vaethyr vith , sui firn pain;
Nallant 'I vrennil vain ben-dihenad
Si baugla le.'
Cennin i nêf thairn hýn,
Nan gortheb pith edrannen pann,
Ar echui nin hirnin si,
Nan dalad amon ring.
Ar sen an darthon hi,
Erui reniol ar nimp,
Ir thâr pellen uin ael
Ar ú-linnar in aew .
1. Natowa kitandawili / mwenye jawabu kutowa
Wako watu sura mbili / majaraha yasopowa
Kuchupa kwao kuwili / nyoyo zao zaunguwa
Watakayo ni muhali / milele hayatokuwa.
2. Akili zao ni ghali / kutu zinawasumbuwa
Wapigana na makali / mwenye fani hupekuwa
Warejea ya awali / hawavuki zao puwa
Wala hawana muhali / wamegeuka viluwa.
3. Wanapeta pili pili / ungó wao chandaruwa
Upungufu wa akili / ukweli kuutambuwa
Wasemavyo waawali / wengine wajisumbuwa
Hatari yawakabili / kuviwasha vilopowa.
4. Mkahawa sihoteli / kushindana kutambuwa
Dibeti zisoukweli / mtuno wakitumbuwa
Kisu kutiwa makali / mwerevu anang´amuwa
Ukweli muukubali / mwiko mwenziwe upawa.
My impression is, looking at preview, to see how markings look on page, that except for ubiquitous w, Swahili got less marks than Sindarin.
On the other hand, if one were to take a Quenya text or even an earlier Qenya text, Fíriel's lament, for instance, it would get more marks for incompatibility with Swahili, due to consontant groups not found in these languages and due to some final consonants, where Swahili ends all words in vowels, than from Sindarin.
Note there are other levels of phonetic similarity than phonotactic compatibility. A word like nyoyo, if respelled nyoio, could theoretically be a quenya word, but not very typical. A word like hayatokuwa could more easily be Japanese than Quenya. Kisu rhymes with Finnish sisu and could more easily be Finnish than Quenya. But hayatokuwa could be (early) Quenya, just as it could be Japanese and is actually Swahili. And kisu could be Quenya, just as it could be Finnish and actually is Swahili.
But I think we have spotted an origin of the Quenya future ending, if Swahili -(u)wa ending* (whatever it means, it may be sth totally other than future of verbs) has a similar sounding ending in Sesotho - or if JRRT ever looked in Carl Meinhof's books on Bantu languages (Swahili, Zulu and Sesotho).
Note, I am not claiming Quenya is in the ordinary linguistic sense of the word related to Swahili. But neither is Sindarin to Welsh. Neither is Quenya to Finnish. Neither is Quenya to Classic or Homeric Greek. I am making a claim about sound similarities, just as Tolkien himself made about Welsh for the one, and about Finnish and Greek for the other.
Tolkien could have been merely mistaken and I can be merely mistaken. Or Tolkien could have been right, and I can be right.
There is no philological proof of the direct kind used by those considering that Nase and nasus have a common (presumed proto-indoeuropean) origin. Because these suppose both sound and meaning and regular correspondences in sound. This lack of proof is both a weakness in my proposition - and in Tolkien's autobiographical claim of having based Sindarin phonology on Welsh.
The next level to look at is of course to look not just at compatibility, which I did here, but also on relative frequencies. I have not marked the monosyllables of Sindarin as incompatible, unless the final consonant or consonant group is outside Quenya (in that position). But their relative frequency is un-Quenya in Sindarin, but not in Swahili, if anything their near absence is somewhat less un-Quenya.
As of course, Swahili's absence of words ending in consonants.
Note that I am doing this on a purely phonetic level. I have forgotten most words I knew from Fauskanger's Quenya course, I have not mastered Sindarin, and I have no idea about Swahili except the kind of generalities that I can gather from encyclopedial articles about it (class prefixes repeated between subject, verb, adjectives, these distinguishing living and intelligent from animal and plant, but not male from female, etc) - and the samples I see from a phonetic view. So, I have no way to immediately understand the words.
If you wish to look at content, for La belle dame dans merci it's just a question of looking up the English version. For the poem in Swahili, it may be more difficult. Unless you know a speaker. I tried Google translate, it didn't work at all for some halflines.
Hans Georg Lundahl
BU de Nanterre
St Narn of Bergamo
* Cautiously here including derivational morphemes in "endings" ...