From Ottoman Turkish بولوت, بولوط (bulut, “cloud”), from Proto-Turkic *bulït (“cloud”). The *-t is hypothesised to be an ancient plural suffix by Doerfer.
Compare Old Turkic 𐰉𐰆𐰞𐰃𐱃 (b¹ul¹it¹ /bulït/), Chuvash пӗлӗт (pĕlĕt).
The computing sense is a semantic loan from English cloud.