Occasionally, the associations of a word become more powerful than its meaning. The history of rapeseed oil provides a glorious illustration of this fact.
The oil from the rape, a variety of turnip, has been in use since the 13th century. It was used as a lubricant called simply rape-oil until the mid 20th century. During World War II it was widely used as a lubricant for steam engines in ships.
Over the centuries, however, several words have merged into the spelling of rape, including one referring to the administrative districts of Sussex, England, a usage that continued until the end of the 19th century. Another, referring to the refuse of wine-making came from French râpe “grape stalk” from Old French rasper “to scrape”, source of English rasp.
The verb (from Latin rapere “to seize”, the origin of English raptor) orginally simply meant “to force”, as in The Rape of the Lock by Alexander Pope. However, as it made its grimy way to its current meaning, all the homophones of the verb receded into the shadows.
The oil of the rape (from Latin rapa “turnip”, Rübe in German), however, was discovered to be low in cholesterol by Canadians after World War II, and they developed a type that was not only fit but healthy for human consumption. By the middle of the 20th century, however, marketing this oil even as “rapeseed oil”, was out of the question due to the new overbearing sense of the verb. Call in the marketers.
The result was that a new name was created for this very healthy oil from the phrase “Can(ada) o(il,) l(ow) a(cid)”, which is to say, canola.