LSJ
οἱ, the Hyperboreans, a people supposed to live in the extreme north, h.Hom. 7.29, Pi. P. 10.30, Hdt. 4.32 sq., Str. 15.1.57. Adj., τύχη ὑπερβόρεος, prov. of more than mortal fortune, A. Ch. 373 (anap.). (ὑπερβόρειος is a constant v.l. in codd. ; but in the poetic passages ὑπερβόρεος is either necessary or at least admissible, as in Cratin. 22, and this form is found in IG2². 1636.8.)
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)