What is a Merkaba, its source, and how does it relate to the Kabah in Mekkah Saudi Arabia?
Merkabah or Markabah مركبة -in Arabic language- is a -feminine- word referring to an object that can be ridden as it comes from the root or verb رَكِبَ (rakiba) to ride. It may refer to a ship a chariot or even a spacecraft. In the Qur'an this verb was mostly used in context of ships see for example in (11:42), (18:71) and (29:65) where it mostly appears in the story of Nuh () with the exception of the story of Musa () and al-Khidr () in surat al-Kahf.
The quran also uses other derivatives such as الرَّكب which is referring to a big amount of people riding animals etc. like a caravan (8:42) and the word رِكَاب which is a synonym of camel (59:6).
Note that the verb (rakkaba) رَكٌّب usually means to assemble and has a different root, so don't confound them.
Al-Ka'abah الكعبة in Mekka is named or is a -feminine- derivative of it's geometrical form المكعب (al-Muka'ab) a cube!
Merkabah and Kabahtallah are in opposition to each other, Merkabh represents a constitution (Way) practiced by the pagans in racism, self centered by faith, and Kabahtallah represents a constitution, based on and commanded by Allah (St), Al, The, La, Limit, h most high, The Lord, in accordance to the creation, The truth (Allah (St) as its foundation to enjoy life within Islam, limit of perfection, the truth.