Note kindly supplied by Larch Garrad, of the Manx Museum, November 1988:

‘A new resident on the Isle of Man approached me recently with a request for the botanical name which he had been told by Port St Mary fishermen used (as he delicately phrased it) “rub on themselves to get themselves a bit excited”.  His version of the Manx name sounded to me like Bossan Mollagh Moar = big soft head, which is Senecio doria [golden ragwort], the herbalists’ garden Saracen’s woundwort, which persists in several places.  I had never discovered the Manx  charmers’ use for it.

However, the director of the Manx Museum subsequently received a telephone call from a well-known researcher  of Manx folklore, John Quilliam, a trustee of the Museum.  Although he was offering information about the plant he insisted that he wanted to speak to the director, a man.  To him was revealed the fact that the same new resident had approached him for help and he had recognised the plant as sun spurge, Euphorbia helioscopia, in Manx Lus y Bwoid Mooar, which Manx speakers who checked the names for the recent Flora had interpreted as ‘the plant of the big knobs”.  This I had accepted as a reference either to its well-known as a wart cure, or to the flower’s structure.

John Quilliam subsequently provided detailed information.  The name, he corrected, properly means  “the plant of the big penis” , but it should be noted that bwoid is also used in other contexts to mean a stout projection, e.g. Bwoid Suggans, the projecting stones to which the ropes securing Manx tied thatch are affixed.  The milky juice of sun spurge was applied to the human penis, and promptly produced considerable swelling.  If this caused excessive discomfort the organ could be dipped in milk (soured milk was usually recommended).  He had several anecdotes and sources concerning widespread use amongst the Manx in the late nineteenth to early twentieth centuries, most commonly by foolish youths larking about.  The care by all concerned that I should not be embarassed was noteworthy

Is this a genuinely traditional use or have those without Manx interpreted a name with a different connotation to suggest such a use and found by experiment that it worked?  Herbals I have consulted were silent, but Geoffrey Grigson [in his Englishman’s Flora, 1987] lists Saturday-night pepper as a colloquial name, without comment.  Was sun spurge the British answer to Spanish fly?

Images:  weed in Promenade flower beds, Douglas, Isle of Man, September 2023.

Updated 18 September 2023.