Genesis 1:8

ויקרא אלהים לרקיע שמים AND GOD CALLED THE EXPANSE HEAVEN — The word “שמים”, Heaven, may be regarded as made up of שא מים “Carry water”, or שם מים “There is water”, or אש ומים “Fire and water”. He mingled fire with water and of them He made the heavens (Chagigah 12a).

וַיִּקְרָ֧א אֱלֹהִ֛ים לָֽרָקִ֖יעַ שָׁמָ֑יִם וַֽיְהִי־עֶ֥רֶב וַֽיְהִי־בֹ֖קֶר י֥וֹם שֵׁנִֽי׃ {פ}

And God called the firmament Heaven. And there was evening and there was morning, a second day.