It seems to me that both adab and aadaab share the same root in speech and original meaning, but have diverged through time, distance and cultural reintepretation. Yet, a very fine gesture still in both cultures anyway (The not particularly western handshake does not meet this.). But this is close to the third-best have, invoking only a different second-best attempt to the first-best transcedent communication. But back on earth, I’m puzzled a bit who and in what relation the involved Yousef is. Your brother cannot be blamed, let alone his age then, for the striking shift.
So here prooves your mundane example story a stepstone to almost all other shifts and misinterpretations throuhout space and time, casting us civilised and heavenly favoured humans back into develish cursed savages – from paradise banned. The road back, through prose or poem, in rythm or ryme, is twisted, curled and endless. Thanks Shaahayda! Bliss on your path.