first cousin once removed
noun
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A parent's first cousin.
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A first cousin's child.
maternal aunt
noun
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A sister of one's mother.
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A sister-in-law of one's mother; the wife or ex-wife of a maternal uncle.
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A similar great aunt, etc.
How often have the words first cousin once removed and maternal aunt occurred in a corpus of books? (source: Google Ngram Viewer )