The word ᴱN. gara “throat” (archaic †garg) appeared in Early Noldorin Word-lists derived from primitive ᴱ✶go, where the long syllable ṝ became ar (PE13/144). Compare this to ᴱN. griw “alimentary canal” from primitive ᴱ✶grgu-, where with short syllabic ṛ the result was gri-.
Conceptual Development: G. cwerc “throat” from the Gnomish Lexicon of the 1910s might be a conceptual precursor (GL/28), perhaps from primitive qṛk-, though elsewhere in the Gnomish Lexicon, qṛ- > cur-, as in ᴱ√qṛđ > G. curdhu (GL/28).
A word appearing as G. garob “cloak, outer garment” in the Gnomish Lexicon of the 1910s with a Qenya cognate ᴱQ. karàpe and a plural form garobin (GL/37). Tolkien initially said the older and more correct form of the plural was garbin, but he deleted this. Since initial voiced stops were unvoiced in Early Qenya (PE12/17) and a often became o in unstressed final syllables in Gnomish, the primitive form was probably ✱gárape. The form ᴱN. garob “rope” reappeared in Early Noldorin Word-lists of the 1920s (PE13/144). It is possible that N. carab “hat” from the 1940s was related conceptually (WJ/187).
Neo-Sindarin: As we have no Sindarin words for “robe” in Tolkien’s later writings, I’d retain ᴺS. garob “robe, outer garment” from primitive ✱gárāpē, a variant of the primitive form of N. carab “hat”, meaning “outer garment” as opposed to “upper garment” = ✱karapē “hat”.