"Is the proposed Arabic etymon the same word as the Ka'aba in Mecca?"

Very interesting question, Mr Bingley. No two dictionaries I consulted offered the same etymology. What does seem certain is that the initial consonant is different in all the proposed Arabic source words: i.e., the voiceless uvular stop usually transliterated as q, versus the voiceless velar stop k in Kaʕaba which is usually glossed as 'cube'. It's in the middle of the proposed Arabic source word that things get fuzzy. In Kaʕaba that backwards looking dotless question mark is a voiced phayrngeal fricative. In the other words, it's everything from two foot signs '' to an h.Glosses are 'to repeat', 'brownish color'. So, off hand I would say no, but who knows. (NB, I am not a Semitic philologist.)

Ceci n'est pas un seing.