Proto-Turkic: *ăl
Meaning: 1 lower side, below 2 (as adj.) being below , lower
Russian meaning: 1 низ, нижняя сторона 2 нижний
Old Turkic: altɨn 2 (Yen. ПМК 90, OUygh.)
Karakhanid: altɨn 2 (MK, IM), alt 1 (\X<1.193>Tefs.\x)
Turkish: alt 1
Tatar: alt 1 (dial., ЯБТ 126)
Sary-Yughur: altɨ 1 (ЯЖУ 14)
Azerbaidzhan: alt 1
Khakassian: altɨ 1
Shor: altɨ 1
Oyrat: ald 1, altɨɣɨ 2; altɨ 1 {(Баск. Туба)}
Halaj: a[:]lt 1
Chuvash: old(ъ) 'gusset'
Yakut: alɨn 1
Dolgan: alɨn 1
Tuva: a'ldɨ 1
Tofalar: aldɨn 'в низовье реки' (Рас. ФиЛ 153)
Kirghiz: ald(ɨ) 1
Gagauz: alt 1
Karaim: alt 1 (K)
Comments: VEWT 14, ЭСТЯ 1, 140-141, Stachowski 32. VEWT confuses (after Bang and Brockelmann) the roots *al- 'below' and *āl 'front'. They are indeed mixed in Kirgh. and Oyr. lit., where we have ald 'front, below', but are distinguished in dialects (Tuba: ald 'front', with a voicing in the consonant cluster after an old long vowel, but altɨ 'below'). The Chuv. form probably goes back to the compound *koltuk altɨ 'axillary concavity, gusset' (attested in Tur., Gag., Az., see Дыбо 154). Most languages reflect *al-tɨ- (the simple form al is not attested, see the discussion in EDT 121), but the reality of the root *ăl is proved by a different derivative in Yakut. Cf. also Sib.-Tat. alaša 'low, low place' (КСТТ 100). Another possible old derivative in -čak may be PT *aĺ(č)ak (Karakh. ašaq, Turkm. ašāq etc., see ЭСТЯ 1, 214-215) 'below, bottom part; low, humble': its traditional derivation from *āĺ- 'to cross (a mountain)' is unsatisfactory both phonetically and semantically. A certain problem is the attribution of the adjective *al-čak (see ЭСТЯ 1, 143-144, EDT 129). Older occurrences of alčaq (MK, KB, Tefs., Rabg. etc.) present the meaning 'modest, humble'; cf. also Sib.-Tat. alcaq 'valetudinarian' (КСТТ 101), Turkm. alčak 'affable' and perhaps Tur. alčak 'mean, vile', alča- 'to offend, humiliate'. This group of forms may in fact reflect a different root, otherwise represented by PT *Alɨg, see under *ā̀le 'weak, tired'. Another group of forms - Chag. alčaq 'bas' (Pav. C.), Tur., Az., Crim.-Tat. (and Oghuz texts like Korkut) alčaq 'low, low place' probably represents an Oghuz innovative derivation in -čak from the root al- (which is why -lč- did not yield -š- here), perhaps influenced by Mong. alča-gar, alča-n 'stunted, undersized', derived from Mong. alčaji- 'to spread legs apart'.
