Tending to crumble or break apart easily; having a crumbly or friable texture.
From 'cram' or 'cramble' plus the adjectival suffix -ly; the 'crumb' association may have reinforced this variant.
English has multiple words for things that fall apart—crumbly, friable, tender—and 'crambly' is the regional cousin that didn't make the dictionary cut.
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