Comprehensive though the list of phobias in the *Oxford English Dictionary* (*OED*) is, it omits some, notably gelotophobia. Nor does it include gelotophilia, katagelasticism, or gelasmus.

The IndoEuropean root KLEG meant to cry out or make a sound, an onomatopoeic form. In Greek κλαγγή* *(pronounced klangē) meant any sharp noise, such as the twang of a bow or the scream of a bird, specifically a crane. The future of the corresponding verb, κλάζω, was κλάγξω (klanxō), I shall scream, from which the makers of an early car horn derived a brand name, Klaxon.

In Latin the verb became clangere, from which we get clang and clangor, clack, click, and cluck, clank, clink, and clunk. Clinkum-clankum, later shortened to clink-clank, being a reduplicated form, signified a succession of clinking sounds and hence a senseless jingle.

To clink means to make a metallic sound, like the sound a clock might make when its hammer strikes a bell. A clinch or clench was a nail or bolt that would make such a sound when struck with a hammer. A clincher or clinker clinched the bolts in ship-building by bending them back or flattening the points. A clinchpoop may have been one who did that on the poops of vessels, and it then came to mean a rough worker or a boor, just as a clown was originally a peasant, giving us a putative link to laughter, which also comes from KLEG.

Latin clangere led to various Northern European forms, such as hlahtar (Old High German), hlakkia (Old Frisian), hlaeja (Old Norse), and hlaehhan (Old English), all meaning to laugh. The Old Irish word cluiche meant a joke. In German gelächter means laughter.

KLEG is an extended form of the IndoEuropean root KEL, to shout or resound, giving the Greek word for laughter, γέλως. Γελωτοφυλλις was the Greek name for *Cannabis sativa*, presumably because it was a plant (φυλλις) that excited laughter.

The *Oxford English Dictionary* (*OED*) lists only a few English derivatives of γέλως and related words. A gelasin is a dimple in the cheeks produced by smiling. Geloscopy, according to Nathaniel Bailey’s *Dictionarium Britannicum* (1730), is “a sort of Divination performed by means of Laughter; or a divining any Persons, Qualities or Character, by observation of the manner of his Laughing”. And a gelotometer is a gauge for measuring laughter. Gelastic means “serving the function of laughter, risible” and gelastics are remedies that act by eliciting laughter, perhaps with Humphry Davy’s laughing gas (nitrous oxide) in mind.

However, the *OED* does not refer to gelastic epilepsy, seizures that result in laughter, a term coined in 1957, nor to gelastic syncope, fainting caused by laughter. When Robin Ferner and I reviewed the benefits and harms of laughter in 2013, we found 1335 reports of pathological laughter; many were due to seizures (Table 1). Gelastic syncope is rarer.

There are other words, not found in the *OED*. Gelotophobia is fear of being laughed at. The earliest hit in PubMed is from 2010, but earlier instances can be found. For example, in 1996 the German psychoanalyst Michael Titze referred to the Pinocchio Complex as “a phenomenon that refers to those with gelotophobia, … people [who] have never learned to appreciate humor and laughter positively.” He suggested treatments. Gelotophilia, joy at being laughed at, is a later coinage, as is katagelasticism, joy in laughing at others (Greek κατάγελως, derision or a laughing-stock). And older than any of these is gelasmus, spasmodic laughter; it was listed in the *Encyclopedia of Aberrations*, which was edited by Edward Podolsky in 1953 and described by one reviewer as “an aberration in encyclopedias”.

The Greek word γελωτοποιός meant, and still means, a maker of laughter, a buffoon. Gelotopoietic should mean stimulating laughter, but I haven’t found it anywhere. Time to introduce it to describe the quality of stand-up comedians.

Finally, back to click-clacking. In French claque means a clap of the hands, and in English an organized body of applauders in a theatre. The claque in the Milan opera house La Scala, the *loggionisti*, who occupy the gods, the *loggione*, can make or break an opera singer. Ronald Reagan once told a story about Leoncavallo’s opera *I Pagliacci* (“Clowns”). A tenor, newly recruited to the company, performed the famous aria “Vesti la giubba” (“On with the motley”). The claque demanded encore after encore: “You’ll do it until you get it right.”

**Jeffrey Aronson** is a clinical pharmacologist, working in the Centre for Evidence Based Medicine in Oxford’s Nuffield Department of Primary Care Health Sciences. He is also president emeritus of the British Pharmacological Society.

**Competing interests:** None declared.

○ ABA numbers have the form A × B ^{A}; 288 is an ABA number since it equals 2 × 12^{2}. [Not to be confused with, for example, “Dancing Queen”, which is an ABBA number.]
○ A powerful number is one that is divisible by the squares of each of its prime factors. ○ The prime factors of 288 are 2 and 3, and 288 is divisible by both 4 and 9, so 288 is a powerful number. ○ An Achilles number is one that, like the Greek hero Achilles, is powerful but not perfect, i.e. not a perfect power. ○ For example, the powerful number 216, whose prime factors are 2 and 3, is divisible by both 4 and 9. It is also a perfect power, 6 ^{3}, and is therefore not an Achilles number.○ However, the powerful number 288 = 2 ^{5} × 3^{2}. It is not a perfect power and is therefore an Achilles number.
○ A Cunningham number is one that can be expressed as a perfect power ± one. ○ 288 = 17 ^{2} – 1.
○ The factorial of a number n, denoted by the symbol n!, is the product of n and all smaller numbers: n! = n × (n–1) × (n–2) … × 2 × 1. ○ Jordan-Polya numbers are products of factorials. ○ 288 = 0! × 1! × 2! × 3! × 4! [0! = 1 by definition] ○ Because it is the product of consecutive factorials 288 is also called a superfactorial.
○ 288 is the perimeter of the right-angled triangle with sides 32, 126, and 130. ○ 288 is the long arm of the following right-angled triangles: 34, 288, and 290 84, 288, and 300 120, 288, and 312 216, 288, and 360 and the short arm of the right-angled triangle 288, 540, and 612.
○ The prime divisors of 288 are the consecutive primes 2 and 3 (288 = 2 ^{5} × 3^{2}). Numbers whose prime factors are all no higher than a specified prime, p, are called p-smooth. Thus, 288 is a 3-smooth number; 3-smooth numbers are also called harmonic numbers. See also Interesting integer 270.
○ multiply 288 by the sum of its digits, 18: 288 ×18 = 5184, which is a square, 72 ^{2}○ divide 288 by the sum of its digits, 18: 288 / 18 = 16, which is a square, 4 ^{2}, and a fourth power, 2^{4}○ multiply 288 by the product of its digits, 128: 288 × 128 = 36884, which is a square, 192 ^{2}○ multiply 288 by its reverse 882: 288 × 882 = 254016, which is a square, 504 ^{2}
○ 2 consecutive primes: 139 + 149 ○ 11 consecutive non-primes: 20 + 21 + 22 + 24 + 25 + 26 + 27 + 28 + 30 + 32 + 33 ○ 2 consecutive odd numbers: 143 + 145 ○ 4 consecutive odd numbers: 69 + 71 + 73 + 75 ○ 6 consecutive odd numbers: 43 + 45 + 47 + 49 + 51 + 53 ○ 8 consecutive odd numbers: 29 + 31 + 33 + 35 + 37 + 39 + 41 + 43 ○ 12 consecutive odd numbers: 13 + 15 + 17 + 19 + 21 + 23 + 25 + 27 + 29 + 31 + 33 + 35 ○ 16 consecutive odd numbers: 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23 + 25 + 27 + 29 + 31 + 33 ○ 3 consecutive integers: 95 + 96 + 97 ○ 9 consecutive integers: 28 + 29 + 30 + 31 + 32 + 33 + 34 + 35 + 36 ○ 288 is therefore a trapezoidal number twice over (see Interesting integer 278 and 279); this also shows that 288 is the difference between two triangular numbers in two different ways: T _{97} – T_{94} = 4753 – 4465 = 288T _{36} – T_{27} = 666 – 378 = 288○ eight consecutive non-primes: 32 + 33 + 34 + 35 + 36 + 38 + 39 + 40 ○ 15 consecutive non-primes: 9 + 10 + 12 + 14 + 15 + 16 + 18 + 20 + 21 + 22 + 24 + 25 + 26 + 27 + 28 ○ 3 cubes: 2 ^{3} + 4^{3} + 6^{3}○ 3 fourth powers: 2 ^{4} + 2^{4} + 4^{4}○ 2 distinct powers of 2: 2 ^{5} + 2^{8}
^{5} × 3^{2}. Now add one to each of the indices of the prime factors (in this case 5 and 2) and multiply them: 6 × 3 = 18. So 288 has 18 divisors. And 18 divides 288 exactly (288/18 = 16).
^{2}(n + 1)/2, where n = 8.
^{rd} entry in Aronson’s sequence. |