Etymology

At least two hypotheses exits, none are explicitly mentioned in the Bible:

• From י ‎(yi, “one of the letters of the Tetragrammaton – a theonym for God”) +‎ שַׁי ‎(sháy, “gift, present”), thus "God's gift".
• From יֵשׁ ‎(yésh, “there is, there exist(s)”) +‎ י ‎(“one of the letters of the Tetragrammaton – a theonym for God”), thus "God exists".