kick
踢 centers on striking with the foot: a kick. It is a specific action of thrusting the leg to hit something.
踢 combines 足 (foot) with 易, which likely contributes the sound. The character is formed to express kicking with the foot.
The left side 足 means foot, and the right side 易 looks like a leg swinging out. Picture a foot swinging out to kick something.
For テキ, imagine a kick so powerful it leaves a 'tech' mark on the target: tech -> テキ, and the foot 足 delivers the kick.