FROM STRONG’S HEBREW DICTIONARY (1890)

Strong’s Hebrew Dictionary (1890) — public domain, printed whole.

shamayim shaw-mah'-yim — dual of an unused singular shameh {shaw-meh'}; from an unused root meaning to be lofty; the sky (as aloft; the dual perhaps alluding to the visible arch in which the clouds move, as well as to the higher ether where the celestial bodies revolve):--air, X astrologer, heaven(-s).