The Oxford English Dictionary writes:
Originally in African-American usage: (as a general term of approval) admirable, excellent. Cf. hot adj. 12c.
Popularized among jazz musicians and enthusiasts in the late 1940s
The first example they give is from the 1930s:
1933 Z. N. Hurston in Story Aug. 63 And whut make it so cool, he got money 'cumulated. And womens give it all to 'im.
The entry refers to hot as a comparison--the main entry is "Characterized by intensity or energy, in a positive or neutral sense (cf. sense A. 9); exciting, fast, successful, etc." and the related sense is:
colloq. (orig. U.S.). Extremely good, splendid; very skilled, knowledgeable, or successful. Also with on and a specified subject or activity.
This is first noted from the 1800s:
1845 in G. W. Harris High Times & Hard Times (1967) 52, I am a hot hand at the location of capital letters and punctuation.
So, it looks like cool developed to mean the same thing as the earlier slang hot in African American English. There is no explanation of why this occurred.
The London slang ends probably came from Jamaican slang, where it seems to have been more generic or local.
The London Slang Dictionary Project ("written by teenagers for their peers and
for their teachers") includes:
Ends - Area, neighbourhood
From ends — one who is “from the streets” and so knows what’s going on.
The second highest definition in Urban Dictionary is the London one:
your 'ends' is your area
"what ends you from?"
by §håÐðw May 21, 2004
A similar meaning can be found in this Jamaican Slang Glossary:
Ends- A place. Mi a go pon one ends still.
(I am going to one place).
And in Backayard Magazine's patois guide:
ends, colloq. home, familiar place.
Another Urban Dictionary definition includes both London and Jamaican meanings:
Jamaican word for street corner
London word for dodgy area
Mi pon di ends (Quote from Dwayne of the Verne)
Rah, SE22? You on the ends bruv (quote from Andrew of SE5)
West Norwood? Wha yah wanna move there to, thats verging on the ends man (quoute from Philly of SW16)
Related words: hood ghetto yard briccie peckz
by bombskwad - detonating warfare wiv lyrics Sep 22, 2006
The W?Dictionary of
Jamaican Dialect i.e. Patois says:
Ends: (n.) Hang out spot/area, place to chill,
(v.) ends out: the act of hanging out
Finally, Talk Jamaican says:
ends : destination, home (pon de ends = at home)
Some of these Jamaican definitions say ends is a destination, so the place at the end of a journey.
Best Answer
It is commonly referred to as merit and stems from the rarity of gold and its use in medallions such as "Gold Medals." (Even this very Q&A board uses Gold / Silver / Bronze in its token system)
It is closest described as "priceless" when used in the context you described.