“The origin of Proto-MSA *γrb ‘to know’ is uncertain. The only immediate parallel is Sab.
γrb ‘to know, to be aware of, recognize’, but one may wonder whether this sparsely attested verb is autochthonous in Sabaic. Comparison with Arb.
ˁrf ‘to know’ accepted in LS and elsewhere implies two phonological irregularities and can hardly be appealing. Shall one tentatively
suspect an ultimate connection with PS
*ˁrb/*γrb ‘to come, to enter’ (“to come across” > “to learn”)? For a recent attempt to connect Proto-MSA *γrb ‘to know’
with Arb. γarīb- ‘strange, unusuaľ and semantically similar lexemes within and outside Arabic v. Bulakh 2013b.” (Kogan 2015:542)