Can someone british explain these slang words please?

[Erik]

Ive seen this on twitter by british users and always wonder what they mean or stand for:

Uno
Una
Oi
Kmt
Buff
Peng

[zarkovnershton]

Uno - This can mean either "you know" or number one.
Una - This can also mean number one, or "use no abbreviations/acronyms".
Oi - This is the British equivalent of "hey".
Kmt - This means "kiss my teeth".
Buff - This means physically fit or strong.
Peng - This is an endearing term, like sexy, hot, beutiful, etc.

[Crazy and Insane]

I cant answer all but
Oi is like hey!
Buff means well built and toned, its referring to physical attributes.

The others are probably internet slang.

[north-west]

Buff means stocky
Oi is hard to explain doesn't really mean anything sort of like "ok" or "ow really" for example "that lads a player" you could reply "oi"

The other stuff is just utter bollocks doesn't mean anythin