Kinetic energy is the energy of motion.  This means that any equation for kinetic energy (KE) must contain mass and velocity.

We will start with two separate equations and put them together...
 
 

work = force*distance Vf2 = Vo2 + 2ad
w = f*d
divide by 2, get ad = Vf2/2 - Vo2/2
since f = ma, w = mad
multiply by m, get mad = mVf2/2 - mVo2/2
notice we have "mad" in each equation, combine these to get...
W = mDv2/2
so,  when a force changes the motion of an object, work is done.  We know that moving objects can do work on other objects, so we refer to  mv2/2 as the KINETIC ENERGY of the object.
KE =  mv2/2
This is referred to as "translational KE" because only objects moving from place to place have it.