Hungarian Historical Phonology atval
(arch.) atval 'Stiefvater'
(arch.) fial 'Stiefsohn'
First attestation/Old Hungarian data
The word appears only in early Hungarian.
Important dialectal forms
Not attested in modern dialects.
Uralic/Ugric/Pre-Hungarian reconstruction
? Proto-Ugric *walə
UEW: *walɜ 'place, space; Platz, Stelle'
Status of the Ugric etymology
Uncertain
Loan etymology
None suggested
Cognates suggested in earlier research
UEW:
Khanty: East (V) wălə 'Platz, Fläche; Lagerstatt, Bett', South (DN) wăt 'Stelle; Spur', (Kr) ewə-wăt 'Stieftochter (für die Stiefmutter)', păχ-wăt 'Stiefsohn (von der Mutter her)', North (O) wăl 'Platz, Stelle, Bodenfläche (z.B. eines Hauses, besonders wenn das Haus verschwunden und nur der Platz zu sehen ist)'
Commentary
-val appears only in compounds in (archaic) Hungarian: atval, fial, which makes the assessment of the Ugric etymology difficult. Khanty compounds like păχ-wăt seem like exact parallel to Hungarian fial etc., but MSzFE and UEW note that it is not certain that -wăt in compounds is related to wălə 'Platz (etc.)' (the words are attested in different Khanty varieties, and the compounds with -wăt are found in South Khanty where *l and *t merge).
Khanty vocalism seems to point to Proto-Khanty *i̮ which can reflect PU *a in old -ə-stems (Aikio 2015), so a Proto-Ugric *walə could account for both the Hungarian and Khanty words. However, due to the problems with attestation and unclarities within Khanty varieties, the etymology remains uncertain.
MSzFE also mentions the possiblity that Hungarian -val in compounds is the same word as fél 'half'. While this is semantically possible, it is unclear how Hungarian v should be explained. MSzFE notes that the compounds like atval should be very early (Uralic *p develops into v in intervocalic position).
Conclusion
Proto-Ugric etymology is possible but cannot be considered certain because the word is scarcely attested and there is uncertainty whether all the alleged Khanty cognates belong together.
References
MSzFE: 99-100, s.v. atval: ? PUg
UEW s.v. walɜ: PUg Uralonet