Rapeseed oil is just another name for Canola oil, from the Canola or Rapeseed crop. It derives its name from a Latin word for turnip. It is also related to cabbage and mustard. Canola oil is actually oil from two specific varieties of this plant. Canola is a shortened form of "Canadian oil, low acid." The acid content was why rapeseed oil wasn't in wide usage for cooking. However, when these varieties with low acid were discovered, it became a good alternative to other cooking oils.