azul ou aqzul kif kif,l essentiel on a un propre salut en tamazightThis motivation is obvious in Berber activists' language planning efforts, sometimes to an almost painful degree; English speakers may be satisfied to have a mathematical vocabulary made up almost entirely of Latin and Greek loanwords, but a mathematical lexicon (Amawal n tusnakt) was one of the very first targets of the Kabyle language movement, published back in 1984. It is equally obvious in the activity of the various Arabic language academies, who, while frequently unable to agree on a single translation of a technical term, can generally at least agree that it must look nothing like the English or French equivalent. And it can be felt even at a much less organised popular level; in Tabelbala, when one speaker gave me an Arabic loan as Korandjé, another would frequently pipe up with "No, that's Arabic, not Korandjé" – even in the case of loans as securely established as the higher numerals. And, while it may not be so active in modern Germany or Finland, its after-effects can still be seen there...
(Azul or Aqzul, whatever; the important point is to have a greeting specific to Tamazight)
Now axir, while of Arabic origin (خير "good"), is not actually used on its own as a greeting in Arabic, and has a purely Berber prefix a- attached for good measure. The only reason that it can plausibly be targeted by activists for replacement is the fact that most Kabyle speakers know enough Arabic to spot the etymology. No one is clamoring to replace Punic loans (like agusim "walnut") with purely Berber terms – any more than Arabic academies are trying to replace Turkish loans like جمارك or Persian loans like جزر with purely Arabic terms.
In that sense, puristic replacement is just as much a product of language contact as borrowing itself is. If you find a language in which loanwords are being selectively targeted for replacement by neologisms, the one thing you can be almost sure of is that a significant number of speakers know the language those loanwords come from. Widespread bilingualism tends to make lexicon boundaries a bit fuzzy anyway – is such and such a rare word really part of language A, or just of language B? – and when people try to reaffirm the boundaries, they don't always agree on where to draw the lines.