A very rare or archaic variant spelling or term, likely a variant of 'errata' with disputed or non-standard usage.
This appears to be an obscure or archaic variant possibly influenced by Latin noun endings (-a typically indicates plural or feminine forms in Latin). Its true etymology is unclear.
This word is so rare that even dictionaries barely know what to do with it—it might be a historical variant that linguists documented but that nobody actually uses anymore!
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