"Binjimin, we must make him cry 'Capivi!'"
Stalky & Co., by Rudyard Kipling, 1899
Capivi is British slang, originally used almost exclusively in the phrase 'cry capivi'. It is a corruption of peccavi, Latin for 'I have sinned', and used as a generalized admission of guilt.
The 1905 A Dictionary of Slang and Colloquial English reported that 'to cry capivi' (also spelled capivvy and kapivvy) meant "to be persecuted to the death, or very near it." If you made Benjamin cry capivi you have presumably beaten the truth, or at least a confession, out of him.
Just a decade later, oojah-capivi (now more commonly spelt oojah-kapivvy) was a common way of referring to a whatchamacallit or a thingy. History does not relate if kapivvy was added to the standard oojah as an indicator of frustration, or simply as a set of silly syllables. However, the 'silly syllable' usage is the only one that seems to have even a token appearance in modern English.
Brevity Quest 2016