"Red Sea" is a direct translation of the Greek "Erythra Thalassa" (). The sea itself was once referred to as the Erythraean Sea by Europeans. As well as "Mare Rubrum" in Latin (alternatively "Sinus Arabicus", literally "Arabian Gulf"). The Romans called it "Pontus Herculis" (Sea of Hercules). Other designations include the (alternatively بحر القلزم "Baḥr Al-Qulzum", literally "the Sea of Clysma"), the Coptic ⲫⲓⲟⲙ ̀ⲛϣⲁⲣⲓ "Phiom ̀nšari", ܝܡܐ ܣܘܡܩܐ Yammāʾ summāqā, Somali "Badda cas" and Tigrinya "Qeyyiḥ bāḥrī" (ቀይሕ ባሕሪ). The name of the sea may signify the seasonal blooms of the red-coloured "Trichodesmium erythraeum" near the water's surface. A theory favored by some modern scholars is that the name "red" is referring to the direction south, just as the Black Sea's name may refer to north. The basis of this theory is that some Asiatic languages used color words to refer to the cardinal directions. Herodotus on one occasion uses Red Sea and Southern Sea interchangeably.