“Mars; Comes from the word Mark. The House of Mars is Aries, the symbol is the Ram. RAM is the reverse of MAR. RAMA is another ancient name for God.

Mars was symbolized by the human thumb, the palm of the hand and by the capitol letter “M.”

This is due to the fact that a weapon such as a sword (a seminal Martian symbol) when gripped, sits in the palm, while the enclosing fingers make an M figure over the hilt. Mars was the God of war and aggression.

In Arthurian legend the enemy of Arthur’s Court was “King Mark”.

The other adversary of Arthur, Mordred, is Scorpio where the planet Mars was said to rule prior to the re-discovery of Pluto. We still say that something is “marred” if it goes wrong.”

Source: Astro-Theology Etymology and Sidereal Mythology Tarot Astronomy