One of my favorite classic guitar solos from the 70’s has to be Eddie Van Halen’s Eruption from the 1978 eponymous first album Van Halen. It’s classic status was confirmed in 2009 when it was included as one of the tracks on the Guitar Hero: Van Halen video game, allowing a whole new generation of air guitarists to pretend to be Eddie. And just a year earlier, Guitar Magazine named it the 2nd greatest guitar solo of all time, bested only by Jimmy Page’s Stairway to Heaven.
In the same year that the song Eruption was released, the UK R&B band called Eruption has their biggest hit with the song, I Can’t Stand the Rain, which reached #5 in the UK charts and #18 on the US Billboard charts.
An eruption is characterized by some type of “breaking forth,” and is most often used in reference to a volcanic eruption, which is “the ejection of solid or liquid matter by a volcano, of hot water from a geyser, etc.” (OED).
In contrast, the word irruption is the opposite and defined by the OED as;
The action of bursting or breaking in; a violent entry, inroad, incursion, or invasion, esp. of a hostile force or tribe.
The inward motion as opposed to the outward is what makes the difference between the words, although they are both pronounced the same.
The first appearance in print of the word is in Heinrich Bullinger’s 1577 page turner, Fiftie godlie and learned sermons, in the quote;
In that hurlie burlie and irruption made by the barbarous people.
It can be traced back to the Latin irruptionem, a noun of action derived from the verb irrumpere, which means “to break into,” and it can be furthered analyzed as the prefix ir- meaning “into” and rumpere, “to break.” Contrast this with eruption, which has the same base verb, rumpere, but the prefix e- means “out.”
The Latin rumpere is the base of a number of other English words, including abrupt (ab- prefix meaning “off,”‘ so “to break off”), route (a way or a course, from the Latin phrase via rupta or “broken way”), and rupture (a break or a tear).
By the 20th century, the word had taken on a special meaning in relation to zoology, namely to refer to;
An abrupt local increase in the numbers of a species of animals.
Thus, in A.L. Thompson’s 1936 book entitled Bird Migration, we see;
Apart from all the categories of annual movements, there are movements which occur at irregular intervals in the form of invasions or irruptions… In the spring of certain years the birds have ‘irrupted’ in large numbers.
It’s in the birding world that irruption seems to be used most frequently. However, the decline in its general usage seems to have been started in the mid 1800’s and even the Corpus of Contemporary American English only offers 27 instances between 1990 and 2012.
As a final comment, it’s worth mentioning that even Mark Twain got the words eruption and irruption mixed up. In Life on the Mississippi (1883) he used the phrase, “A firmament-obliterating irruption of profanity,” and in the context, it would seem that he meant an “eruption of profanity.”
Happens to the best of ‘em, I guess.