Napier notes that O.E. PUCA, "a goblin," whence N.E. Puck, is a well authenticated word.
"The Sources and Analogues of 'A Midsummer-night's Dream'"
Compiled by Frank Sidgwick
On the other hand it is incorrect to derive Puck from Irish PUCA, as the latter is undoubtedly borrowed from some form of Teutonic speech.
"The Glories of Ireland"
Edited by Joseph Dunn and P.J. Lennox