LSD - librae, solidi, denarii. Roman coins*, that didn't bear the same relationship to each other, but classical was posh. Richard Gough, in his wonderful early 18th century History of Myddle , asserts that in Shropshire pounds were called 'leawans', a term I haven't come across anywhere else. 'Quid' for 'pound' is apparently attested from the 17th century, long before paper money, so Quidhampton is impossible as an origin. It also makes the Irish origin unlikely. 'Quid' however is Latin for, among various other meanings, 'how much', so something along those lines seems a likely enough origin.

As for chains and furlongs, note that an acre (4840 square yards) is one chain by one furlong- an idealised peasant strip in the mediaeval communal fields. And if you've never seen a peasant strip.....

*Actually the libra was a weight, the coin of that weight was an as, but how could we have called our currency that?