Slang 'Ham'

[Gint Gaidamas]

Hello,

I have a question if anyone can explain the origin of the sports slang HAM?
Why is it written in Capital letters?
Plese see links:
Spoting slang
 http://books.google.lt/books?ei=MZsBT4-CBsjP8gPns53hDw&hl=lt&id=RTdcQOlzjXAC&dq=of+New+York+for+a+second-rate+dude+or+masher%2C+and+more+especially+applied+to+the+habitues+of+the+Rialto+in+that+city.+...&q=ham

http://books.google.lt/books?ei=R-8BT5u-IJHu8QPqqN3SBA&hl=lt&id=QfBZAAAAMAAJ&dq=ham-fatter++ham+sporting+slang&q=hamfatters+ham

Origin by William H. Nugent
http://www.unz.org/Pub/AmMercury-1929mar-00329?View=PDF

Slang of the stage
http://chroniclingamerica.loc.gov/lccn/sn82014381/1881-03-19/ed-1/seq-3/;words=Actors+ham?date1=1870&rows=20&searchType=advanced&proxdistance=5&date2=1885&ortext=&proxtext=&phrasetext=ham+actor&andtext=&dateFilterType=yearRange&index=1

Origin of Ham-fatter
http://query.nytimes.com/gst/abstract.html?res=F00713FF3C5511738DDDAC0894DB405B8384F0D3&scp=1&sq=ham%20fat%20man&st=cse

Best regards,
Gint

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