This is a more inside way of saying you have to drop a deuce (take a crap), it works really well in an office setting so that you may let your close, personal co-workers know where you are going without letting everyone else know. This is derived from John Wayne's nickname being "The Duke", and can be shortened by simply saying "I have to make a phone call", or added to by saying "man John Wayne has been calling me all day."
"I'll be right back I have to make a phone call to John Wayne."

"I'll call you right back John Wayne is calling me on my other line."
by the crab show July 8, 2009
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a common excuse used by faggots on the internet who are getting their shit pwnd
I'd love to hang around & talk about how shitty my boarding is, but I've g2g make some client calls
by skallywagz December 9, 2009
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