These penis caps must have been very uncomfortable - even painful - to wear, from which I can only conclude that part of their purpose was to suppress the 'urges' of the young men as they came of age.
This old and finely made example of an umncedo is woven from Ilala palm leaf, and incema grass. Boys received their penis cap after their initiation into manhood. In the 19th century Zulu society, it was said that a man was not properly dressed unless he was wearing his penis accessory.
For a similar but distressed example acquired by the British Museum in 1866 see: https://www.britishmuseum.org/collection/object/E_Af-3288
And another very similar to ours acquired in 1902: https://www.britishmuseum.org/collection/object/E_Af1902-7
ex Alain Guisson Collection, Brussels