A variant or archaic form potentially related to eruca (a caterpillar or the plant arugula), though rarely used independently.
Possibly a truncated or variant form of 'eruca' from Latin, though the precise etymology and usage are obscure in modern English.
Eruc is so obscure that it barely appears in even comprehensive English dictionaries—it represents a dead-end branch in English etymology where a word started to take hold but never quite made it.
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