What is the origin of the word "quid" for a British pound, and what is the origin of the word "buck" for an American dollar?

The slang money expression 'quid' seems first to have appeared in late 1600's England, derived from Latin (quid meaning 'what', as in 'quid pro quo' - 'something for something else'). Other intriguing possible origins/influences include a suggested connection with the highly secretive Quidhampton banknote paper-mill, and the term quid as applied (ack D Murray) to chewing tobacco, which are explained in more detail under quid in the cliches, words and slang page.
http://www.businessballs.com/moneyslanghistory.htm

The word buck—possibly an abbreviation from "buckskin", an intrinsic "currency" for trade with American Indians known since 1746—has been recorded since 1856 and is widely used as a synonym for the dollars of many countries, including Australia, Canada, New Zealand and the United States.
https://en.wikipedia.org/wiki/Dollar

The real answer needs answered by a gealic speaker.

"Chuid" is Gealic for portion or share. It entered English vernacular in the 1800's with Irish serving in the British military. The Irish referred to their pay as their "chuid" and was Anglicized to "quid" that we still use today. One Pound Sterling equals one Quid (English) or Chuid (Gealic).

https://www.quora.com/Where-does-the-word-quid-come-from