Fo Shankles is used when going on a irate ramble ... you add this word to liven up the situation with some flava.
"CALZONE GET DOWN FROM THAT FO SHANKLES TREE!"
by Vanessa & Olivia September 2, 2005
A.S.N. variation of "fo' sho" or "fo' shizzle".

In order to make it rhyme, as is the case with "fo' shizzle my nizzle", it's often said as "fo' shankle my ankle"

We don't need to give y'all a reason, why do you care?
"So did you plow that bitch yet?"
"Yee, fo' shankle!"
by --Octo-- May 31, 2008