For to pony up, etymonline.com says
1824, in pony up "to pay," said to be from slang use of L. legem pone to mean "money" (first recorded 16c.), because this was the title of the Psalm for March 25, a Quarter Day and the first payday of the year (the Psalm's first line is Legem pone michi domine viam iustificacionum "Teach me, O Lord, the ways of thy statutes").
(which in itself is one awesome etymology if true)
For the more rare, although in use everywhere from Huckleberry Finn to modern San Francisco Chronicle, to pungle (up), Merriam-Webster says,
"Pungle" is from the Spanish word "pongale," meaning "put it down," which itself is from "poner," meaning "to put" or "to place," or more specifically "to contribute money." The earliest uses of "pungle" are from the 1850s
But does that Spanish poner as in "to contribute money" come from the same slang Latin pone?