yessir
Concise Oxford English Dictionary © 2008 Oxford University Press:
yessir /ˈjɛsə, jɛsˈsəː/
▶exclamation informal expressing assent, especially to a superior.
■ N. Amer. expressing emphatic affirmation.
– origin early 20th cent.: alt. of yes sir.
'yessir' also found in these Oxford entries:

