Actually Medievalist is correct in the way Jews spell it...especially from the Yiddish...with a "z"...

(but to each their own)
But neither Lantzman nor Mensch covers it...
Mensch means someone behaved with manners actually
Lantzman as M. said implies someone from one's old home town
Used much more by Polish & White Russian Jews...
Actually Jewish Cemeteries until today have pre-bought plots by those who came to the US and all the Lantzman got together and bought enough land for 100 graves..(Mount Hebron in Queens is one such example)
mmmmm....
lets see
well we dont want to call they "goy" Hebrew for Gentile and has not such nice connotations...
There is a hebrew word slang that is "Achi" used in Israel all over..means "my brother" and everyone uses it with friends...."Hey Achi"...even if you dont know the person..however I would not know if this would ring true between Gentile and Jew...but it is close for it...I cannot see getting into a Taxi in NY and saying to the driver Hey Achi how are you doing? However if he was Israeli, that would be appropriate.
However, Yiddish is a very closed language...rich but closed...and developed during the years of a not so nice and not so friendly exile..so I know of no word that would be used for what you are looking for...
Hebrew...all that comes to mind actually would be Achi - but it would be "Achi" not "Achi Teddy" that would be more like for an informal introcution
"Hey David. This is Achi Teddy" (something like that but not normally used.)
"Achi" is best..if I think of something else I will post it
BTW...Achi is MODERN HEBREW terminology...so if you are looking for something from the past...that is going to be very difficult to come with..
Again..modern Hebrew terminology is NOT used or known by Jews outside of Israel...as well