In the spring following the Great Fire in 1666, Londoners were astonished to see a sudden eruption of a plant they called London rocket. It wasn’t the plant itself they thought remarkable — a close relative of the hedge mustard, rather more than a foot tall, with small yellow flowers — but the vast quantities of it that appeared, growing everywhere on burnt areas. (This was mirrored after the London blitz of 1941 by an unexpected flowering of the purple rosebay willowherb, another adventitious plant of waste places).
You might think that the plant was called rocket because it shot up so quickly, but not so. The name is shared with a number of species of Sisymbrium found in various places throughout the world, all members of the cabbage family, many of which were (and still are) used as salad vegetables. The name came ultimately from the Latin eruca, which was applied to some member of the group, probably colewort (it has been suggested that it comes from eructare, “to belch”, the source of our word eructation, because of its sad propensity to generate wind). It got to us in its strangely garbled form via the Italian ruca (losing its initial letter), whose diminutive was ruchetta, which became the French roquette (still the name for the plant today), and so to English in its modern form sometime in the early sixteenth century.
The Latin eruca has confused at least one writer, as it has two meanings; as well as a cruciferous plant it could also refer to a caterpillar (for example, the English eruciform means having the shape of a caterpillar, but erucic acid is an old name for an acid obtained from mustard and Eruca is the systematic name for some plants of the cabbage family). A small edifice of ingenuity was built up trying to explain how the word for a caterpillar should have been applied to a plant, almost convincing in places.
The salad vegetable had a considerable resurgence in popularity in the early nineties, so much so that people are now bored with it, and it is unfashionable again in all the best places in London (“Darling, how delightfully retro! How 1994!”).
But the most familiar connotation today of the word rocket remains the device that rushes off with a bang and a flash, whether for fun, as a weapon, or as the device that hurls satellites into space. A NASA rocket has this week sent the first scientific satellite to the moon for 25 years, carrying with it a few grams of the ashes of the astronomer Gene Shoemaker, whose greatest regret was that he was never able to set foot there.
This sense of the word comes to us from a quite different source. It derives from the Italian for “spool” or “distaff”, roca, again via its diminutive rocchetto, and was applied to the device because of its long, thin shape. Interestingly, it first appears in English in the early seventeenth century, just at the time when the efforts of a certain Guy Fawkes and his gang to blow up Parliament gave future generations a cast-iron excuse to fire off recreational rockets once a year.