Lunch, being the mid-day meal, much more likely comes from:
launags (Latv.) - afternoon snack;
lȭnag (Livonian) - south-east; lȭnagist (Livonian) - mid-day meal;
lõuna (Est.) - south and mid-day meal;
lounas (Fin.) - south-west and mid-day meal;
lõunad, lõunaz (Votic) - south and mid-day meal;
lounad, loune(d) (Izhorian) - south and mid-day meal;
lounat (Karelian) - evening and main meal;
lun (Komi) - day and daylight;
lun-aǯ́e (Udmurt) - during the day.
There is a further intercrossing of louna vs. luna; and moon vs. noon:
nun, nunal (Udmurt) - day;
南 [Nán] (Chinese), 남 [naam] (Korean) - south;
And here is the fairytale invented for noon: http://www.etymonline.com/index.php?term=noon noon (n.) mid-12c., non "midday, 12 o'clock p.m., midday meal," from Old English non "3 o'clock p.m., the ninth hour," also "the canonical hour of nones," from Latin nona hora "ninth hour" of daylight, by Roman reckoning about 3 p.m., from nona, fem. singular of nonus "ninth" (see nones). Sense shift from "3 p.m." to "12 p.m." began during 12c., when time of Church prayers shifted from ninth hour to sixth hour, or perhaps because the customary time of the midday meal shifted, or both. The shift was complete by 14c. (same evolution in Dutch noen).
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Very likely related to lõuna (Est.) - south and mid-day meal; lun (Komi) - day and daylight - are all words with same stem and depicting light and brightness:
лонщ, лонт [lonsh, lont] (Khanty) – snow;
lov (Erzia, Moksha) - snow;
li̮m (Komi) - snow;
li̮mi̮ (Udmurt) - snow;
lum (Mari) - snow;
lopme (Saami) - snow;
lu’im, lu’m (Livic) - snow;
lumi (Est., Fin., Votic, Izhora, Karel., Vepss.) - snow;
lumine (Est.), luminen (Fin.) - snowy;
lumen (Lat.) - a light, a brightness;
luminous (Eng.), luminoso (It.) - bright, lighted;
luna (It., Lat.), луна [luna] (Rus.) - moon;
luce (It.), ljus (Sw.) - a light;
lum (Sumerian) - to shine.
leimu, loimu (Fin.) - flare, blaze;
lõõm, loimu, lõõsk (Est.) - flaming fire;
leek, leegi (Est.) - flame.
Note that f-, b-, p- are idle prefixes in English flare, flame, blaze, flash, Ital. fiamme, Rus. пламя [plamia], блеск [blesk], and they are also related. According to M.Naddeo, these idle prefixes (protesi oziosi) were studied by the Italian linguists in the 19th Century, but are ignored by the Indo-Germanists (they see these idle prefixes as part of stems of the words, and, as a result, are unable to connect the obvious).
The connection of 'day, daylight, clear sky' (like in Komi, Udmurt lun), and 'south' (like in Est. lõuna), and 'lunch' (like in Est. lõuna) may be similarly observed in:
югъ [yug] (Old Georgian), йагъ [yag] (Megrelian), egun (Basque) – day;
ég (Hung.) - sky, heaven, to burn, to flame;
aeg, aja (Est.) - time, epoche, also day (see for other related Finnic words: http://www.eki.ee/dict/ety/index.cgi?Q=aeg&F=M&C06=et )
Compare also to the four Yugas (or ages) the world went through as part of a 'cycle of yugas' described in the Sanskrit scriptures, each followed by 'the end of the light' cataclisms.
юг [yug] (Rus., Bulg.), jug (Albanian, Bosnian, Slovenian, Croatian), југ (Makedonian, Serbian), juh (Slovakian), jih (Szech) - south; южный [yuzhny] (Rus.) - southern;
egu, hego (Basque) - south;
ужин [uzhin] (Rus.), у́жина, ю́жина [uzhina, juzhina] (Old Bulgarian), у̏жина [uzhina] (Old Serbian), júžinа (Old Slovenian), juzyna (Old Polish), Jause (Old German dialect) - dinner, initially midday meal; uzsonna (Hung.) - snack;
[di] (Sumerian) - to shine; de, di, didal (Sumerian) - flame;
dies, diē, diī (Lat.), dia (Sp.) - day, daylight (Eng.);
день [den'] (Ukr., Rus.), дзень [dzen'] (Belorussian), dzień (Polish), 天 [Tiān] (Chinese) - day;
таң [tang] (Kazakh), dan (Azeri), tan (Turkish) - dawn (Eng.);
täna (Est.), tänään (Fin.), туннэ [tunne] (Udmurt) - today;
taevas (Est.), taivas (Fin.) - sky (see for other related Finnic words: http://www.eki.ee/dict/ety/index.cgi?Q=taevas&F=M&C06=et );
deas (Scottish), theas (Irish) - south;
meridies (Lat.), mediodía (Sp.) – south (literally, midday);
пiвдень [pivden] (Ukr.), поўдзень [poudzen'] (Belorussian), południe (Polish) – south (literally, midday);
တောင် [taung] (Burma) - south;
dine, dinner (Eng.) - to eat lunch, lunch;
полдник [poldnik] (Rus.), полуденок [poludenok] (Ukr.) - midday meal, literally.
dal (Sumerian) - fire; de, di, didal (Sumerian) - flame;
tuli, gen. tule (Est.), tu’ļ (Livic), tuli (Fin., Votic, Izhorian, Karelian), tuľi (Chud'), tuli, tuľ (Vepssian), tol (Erzia, Miksha), tul (Mari), ti̮l (Udmurt), ti̮v (Komi), tu (Nenets, Enets), tui (Nganasan), tǖ- (Sekulpian), tuj (Matori), tűz (Hung.), dolla (Saami) - fire;
dalla, dal, daal (Sumerian) - midday;
dél (Hung.) - south, midday; déli (Hung.) – southern;
giorno (It.) - day;
mezzogiorno (It.) – south (literally, midday);
noon (Eng.) - midday; nun, nunal (Udmurt) - day;
南 [Nán] (Chinese), 남 [naam] (Korean) - south.