Hungarian Historical Phonology hattyú
hattyú 'swan'
First attestation/Old Hungarian data
1282 Hathias (derivative, place name)
See EWUng: 538, s.v. hattyú
Important dialectal forms
[coming]
Uralic/Ugric/Pre-Hungarian reconstruction
Disputed:
Abondolo 1996: 49: *kutëŋV
UEW: *kottɜŋɜ ‘swan; Schwan‘
Status of the Ugric etymology
Unclear
Loan etymology
PUg ← Turkic *kotan
Cognates suggested in earlier research
Khanty: North (O) χŏtəŋ, East (V) kŏtəŋ, South (DN) χŏtəŋ 'swan'
Mansi: North (So) χotaŋ, East (KU) χotəŋ, West (P) kotəŋ, South (TJ) kotā·ŋ 'swan'
Commentary
The Proto-Ugric etymology is presented by most major sources: UEW, EWUng: 539, s.v. hattyú, WOT.
Abondolo (1996) reconstructs PUg *u, and it is true that the Ob-Ugric forms point to *u, showing similar correspondences (Proto-Mansi *ɔ and Proto-Khanty *u in Zhivlov's 2006 reconstruction) as inherited Uralic words like the reflexes of PU *suksi 'ski, snow-shoe'. The reconstruction of the word-internal consonant (*t, *tt?) requires further research: origin of Hu ty is unclear.
It is not clear that Hu hattyú and the Ob-Ugric forms reflect a similar derivative: no good parallels to the development of *ŋ in *kottVŋV > hattyú are known. It is dubious whether a Proto-Ugric word can be reconstructed, and it might be plausible to assume that the alleged cognates in Hungarian, Khanty and Mansi are parallel loanwords from somewhere.
The old idea of a Turkic etymology (supported by Ligeti 1986: 139, UEW, Abondolo 1996) is criticized by Róna-Tas (1988) who notes phonological difficulties in the explanation. WOT (1312) assumes that the words in Ugric and the so called Altaic languages are Wanderwörter. This explanation is plausible, but it seems quite possilbe that the wondering word has been borrowed separately into Hungarian, Khanty and Mansi.
Conclusion
The Ugric etymology remains uncertain because of some phonological problems. It is possible that the words in the Ugric languages are indeed Wanderwörter as has been assumed.
References
Abondolo 1996: 49: PUg ← Turkic
EWUng: 539, s.v. hattyú: PUg ← Turkic
Honti 1982: 158, No 342. POUg *kŏtɜŋ
Ligeti 1986: 139
Róna-Tas 1988
UEW: PUg ← Turkic Uralonet
WOT: 354-355, 1279: PUg, a "Nordic cultural wandering word"
Zhivlov 2006: POug