𒋰 dab₂ double

Duplication of signs and letters very often have special orthographic meaning:

ГГ = NG in gothic
ll = y in Lloret
…

True duplication via 𓏮 (𓅱𓏮 how yaya@Hausa)

True reduplication appears in languages and is different from orthographic duplication discussed here.

There's the lingering question of the elusive "Euphratean" substratum in Sumerian (AKA "Banana language" in reference to reduplication), which some have associated with the Ubaid and Samarra cultures, according to this model the Sumerians' ancestors would have come from further up north and the Uruk culture ought to be viewed as intrusive. Much of this is hypothetical, the ancient DNA would provide some amount of closure.

It appears that the duplication of letters served to indicate full/prolongued/special pronunciation:

Unlike German, which has a similar rule, the whole word or syllable is repeated, not just the vowel.

𓎡 𓏏 𓎡 𓏏 quiet! quuiieet vs chute-chute
𓃀 𓂋 𓃀 𓂋 𓊮 | boil | vs burn फोड़ा phoṛā 𑀨𑁄𑀟 phoḍa फुंसी phunsī pustola פוּרוּנְקֶל furúnkel furie
𓈖 𓆑 𓈖 𓆑 𓈖 𓍢 unwind 𓆑𓈖𓊡 𓍬 vs nvnvn 'unroll' 𓆑𓏲𓏏𓊡
𓊃 𓊃 𓆑 𓂉 | © soothe | syyssin ⋍ soothing doublication BUT:
𓊃 𓊃 𓊮 | ashes |
𓏘 𓏘 𓀁 | eat | കഴിക്കുക kaḻikkuka !
𓏘 𓏘 𓀁 | eat | كل kal 𒅥 akālu
𓏘 𓏘 𓀁 | eat | خردن xarden
𓏘 𓏘 𓀁 | eat | carne ⇔ comar kuman chamo 2:min mangià magnà
𓏘 𓏘 𓀁 | eat | খা kha kauen kaon кваназе kwanaze खाणौ khāṇau खाणे (khāṇe) ماکن makan ᦂᦲᧃ (k̇iin)
ուտել (hy) (utel)
somehow this doubling also encourages a 'ti'/'di' syllable :
𓈖 𓆓 𓊃 𓆓 𓊃 𓊮||burn|incendiar ?
𓃀 𓂋 𓃀 𓂋 𓊮 boil pustola (𓂋=os in latin) ⇔ δοθιήν dothiḗn ?
𓈖 𓇋 𓈖 𓇋 Greeting! namasTe na.du
𓈖 𓊪 𓈖 𓊪 𓏏 𓋳||hem|Naht ⇔ Nabel?
𓅓 𓅓 𓇋 𓈒 𓈒 𓈒 =
𓅓 𓏮 𓈓 =
𓅓 𓏏 𓂺 𓅱 𓏏
☑

𓃀 𓂝 𓃀 𓂝 𓏜 | drink | bebér
𓃀 𓂝 𓃀 𓂝 𓀢 | drink | bebér bibo@Lat ++++
𓃀 𓂝 𓃀 𓂝 𓈗 | drink | boire duplication

𓇋 𓃀 𓃙 𓏏 𓀁 | thirst | lambida ( yb/λb ymb ⇔ λmb limb 𓃀 jamb ) ⇔ 𒆗𒆗𒌅 lap-lap-tu !

𒋢𒂡𒂡 /šeršer/ שַׁרְשְׁרָה šaršərā “chains” @ Kerker
𒉠𒂡𒂡 /šeršerratu/, “chains” 𐎌𐎌𐎗𐎚 ššrt ܫܝܫܠܬܐ šēšaltā շղթայ šłtʿay
𒋢𒂡𒂡 /šeršer/ зунжур zunžur zinxhir زنجیر zanjir “chains” 2

𒂷𒂷 ĝa2-ĝa2 = ĝar

𓈖 𓌰 𓈖 𓅓 𓌰 𓅓 𓂻||quake, quiver, go to and fro|meander < nean.Mean.do
𓏠 𓈖 𓏠 𓈖 𓂻||(earth)quake|meander vs ⇔ za‘za‘a : quake @AR
𓏠 𓈖 𓏠 𓈖 𓂻||be shifted (of boundary)|mWander ⇔ move
𓏠 𓈖 𓏠 𓈖 𓂻||move quickly (of person), move about (of army)|moving

𓈖 𓎛 𓎛 𓇳 𓈇||eternity, for ever|ⲉⲛⲉⲣⲍⲓⲁ < inhouratia ⲉⲛⲉⲣⲍⲓⲁ⋍eternia narration<know

𓅓𓂝𓅓𓂝𓄛 MaMa ⇔ 马⻢ καμηλοπάρδαλις kamēlopárdalis Kamel-Pferd@Afrikaans
𓅓𓂝𓅓𓂝𓄛 shiraapher=𓋴𓂋𓃱 ? mirrored and 𓄛shir(kan) and 𓅓br and doubling

𒀀𒀀𒋻 µWater 𓈗 doubling

See also combining double letters => ___? 𓄿 𓆑 a'F => Fa/Fä/Fe 𓄿 𓄿

𓂋 𓂋 𓇋 𓃟 | boar | bi.ore doubling

𒄥𒄥𒊒 qur-qur-ru χαλκεύς khalkeús calderero
𒄥𒄥𒊒 esp. coppersmith, metal-worker
𒄥𒄥𒊒 •l'gab-qur-ru < LAGAB •cop-qur-ru •qurᵇᶥ-ru doublication

•𒄥𒈨𒌍 ⇔ мыскер mısker مسگر mesgar مِسگەر coppersmiths

𒄩𒊏𒊒 ḫa-ra-ru ⇔ √grab 𒄩 KU₆-ra-bi doubling
𒄩𒊏𒊒 deduct, hollow out, to break off, to dig

𒍣𒆥 zi-qi => syukʿ / zepʿyu / spe doubling

𒆹𒆪𒆪 suk-ku-ku® | deaf | sağır doubling ⇔ silence

𒄰𒄰𒈠𒌅 kam-kam-ma-tu "ring" √krumm doubling

𒈝𒋛𒊒 ḫum'si-ru •kumā' 𓂝 𓅓 𓂝 𓅓 𓏲 𓄛 𓏤 | shrew | ⇔ Hamster Tier ⇔ 鼠 tshr щур ščur

Luwian orthography

https://en.wikipedia.org/wiki/Luwian_language#Cuneiform_Luwian

Compared to cuneiform Hittite, logograms are rare. Instead, most writing is done with the syllabic characters. A striking feature is the consistent use of 'full-writing' to indicate long vowels, even at the beginning of words. In this system a long vowel is indicated by writing it twice. For example, īdi "he goes" is written i-i-ti rather than i-ti, and ānda "in" is written a-an-ta rather than an-ta.
This could also be interpreted as double use of a sign similar to hebrew v/u :
i-i-ti wāte waten "walk"

𓎼 𓃀 𓎼 𓃀 𓀉 𓅪 | be lame | Krüppel

𓂝 𓅓 𓂝 𓅓 𓐢 | container (for bread etc..) | amphore ? doubling

𓍯 𓍯 𓏏 𓍢 cord rrod ⇔ 𓌗 rigid ridge ⇔ rope Reif robber 𓍱 ?

𒊕 Kopf in 𒊕𒁺 qaqadu qaqqadum 𐎖𐎄𐎖𐎄 •qpr/qdqd qoḏqōḏ קָדְקוֹד peculiar
𒅗 KA | kǒu 口 𒅴 kʲap@Luri Klappe "mouth"

𒁄𒁄 barullo brouhaha bruch brut "noise" 𒁄𒁄 boucan brüllen ⇔ bull

𓎡 𓎛 𓎡 𓎛 𓀗 | old | 𒋼𒀀 kar² ghiero : gero γέρων

𒄷𒄭;𒁁 mud;mud₂ 𒄷𒄭 dāmu "blood" reverse daMudama doubling

𒅲𒅲𒅅 mumun-ĝal₂ mumunĝal manaaja ಮಾಂತ್ರಿಕ māntrika "exorcist"

𒁲𒁲 sa₂di sadug

𓉔 𓃀 𓉔 𓃀 𓍁 | knead | 𒋃 silaĝ < دَلَكَ dalaka @ duo-leg

dual r

doubling has special orthographic provenance:

𓏏𓏏 Teti ≈ Tyréis

𒊕𒊬𒊬 saĝ.mu₂mu₂ saĝmu® shimmer shime to shine

𒌨𒌨 ᶱURᵇᶥ 𓊃 𓄿 𓃀 𓃤 siyārᵇ सियार "jackal" Tier
𒌨𒌨 ʸUR.URᵃ יָרוֹרָא yārōrā jackal
𒌨𒌨 ʸUR אִי

𒀀𒀀 a¬a 𓂜 𒀀 a¬ אִי í corroded doubling symmetry

   swine  𓂋  𓂋  𓏏  𓄜  𓏪  
   boar   𓂋  𓂋  𓇋  𓃟  
   sow    𓂋  𓂋  𓅱  𓏏  𓃟  
𐀏-𐀫 ka-ro χοῖρος @GR  

using full 𓂋 χοῖροn ⋍ corn

𓇋 𓐍 𓐍 𓅱 𓇶 | dusk | krēsla ⇔ 𓐍 Kreis

𐘥 KE ≈ ኮከብ kokäb 𓋴 𓃀 𓇼 كَوْكَب kawkab < 𐎋𐎁𐎋𐎁 kbkb kabkab 𒀮 𒀯 kakkabum

𒅗𒅆𒅆 ka-ši-ši Kassierer
𒅗𒅆𒅆 debt-exactor

𒈪𒅎𒈨𒂊 mimmê property ⇔ маёмасць majómascʹ majetek omaisuus менчик mencik
𒈪𒅎𒈨𒂊 mimmê property ⇔ مَال māl مُلْك mulk milk мүлік mülık emlak

𒈣𒁶𒁶 MA₂-GIM ≈ mai gina jirgi ≈ madugu na jirgi ≈ ameyza ughar ≈ mvuvi …
𒈣𒁶𒁶 MA₂-GIM-GIM •MA₂RA-GIM > malāḫim malāḫum ملاح মাল্লা malla amellal galama
𒈣𒁶𒁶 boat-builder, boatman

𒀀𒇉 𒀀𒇉 ÍD-ÍD (nârâti) rivers

𓋴 𓃀 𓍿 𓄑 𓀁 | laugh | ge-baku 𒀀𒅆 bu₄igi 𒁀𒆪𒌋 ba-ku-u bakū كَى bakā בָּכָה bɔḵɔ́
𓋴 𓃀 𓍿 𓄑 𓀁 | laugh | 𒅆𒀀𒅆𒀀 ši.bu₄igi.a #šubakū (to cause to laugh)

𒅁𒋼𒋼 ip-te-te
𒅁𒋼𒋼 open (ed) ⇔ 𒋼𒋼 Tauri ≈ Tür / Tor / door

𒃲𒃲 gal²(min) ≈ Gemini ♊ in 𒋰𒁀 tab-ba ≈ double in
Gemini ♊ 𒀯𒈧𒋰𒁀𒃲𒃲 mul.maš₂-tab-ba.gal²(min) "Great Twins" 🐓

मुर्ग़ा murġāˡ