Meaning

noun a small reddish planet that is the 4th from the sun and is periodically visible to the naked eye; minerals rich in iron cover its surface and are responsible for its characteristic color

noun (Roman mythology) Roman god of war and agriculture; father of Romulus and Remus; counterpart of Greek Ares

noun the month following February and preceding April

originPossibly a variant of Marrs, itself from Marr with post-medieval excrescent -s. The Mars bar was named after Franklin Clarence Mars, who founded the company that produces these chocolate bars.

Etymology from Wiktionary, CC BY-SA 3.0