Hungarian Historical Phonology levél
levél 'leaf'
First attestation/Old Hungarian data
[coming]
Important dialectal forms
[coming]
Uralic/Ugric/Pre-Hungarian reconstruction
? Pre-Hungarian *läpä- or *läwä-
(Disputed:)
UEW: PUg *lȣ̈pɜ (lepɜ) 'leaf, sheet; Blatt'
WOT: *lepə
Status of the Ugric etymology
Improbable (phonologically irregular)
Loan etymology
None suggested
Possible substrate loans (new suggestion)
Cognates suggested in earlier research
Khanty: East (V) ḷi̮wət, South (DN) lipət, North (O) lipət 'Blatt'
Mansi: South (TJ) laptā, East (KU) loptə, West (P) luptə, North (So) lūpta 'Blatt'
Commentary
Although the etymology is considered convincing by most sources (including WOT), the Ugric etymology is completely irregular, and no common proto-form can be reconstructed (also no Proto-Ob-Ugric form can be reoncstructed). If the words in Hu, Kh and Ms are related, we might be dealing with a substrate word borrowed separately into the three languages.
Conclusion
The Ugric etymology should be rejected.
References
EWUng
UEW: Proto-Ugric Uralonet
WOT: 1312: PUg