Well the English version of the bible is a translation from another language. So it would not have said "foot of Christ", in the Latin, it probably said "Pesi Christ".
Foot is from middle English taken from old English or old german.
http://www.merriam-webster.com/dictionary/foot
Origin of FOOT
Middle English fot, from Old English fōt; akin to Old High German fuot foot, Latin ped-, pes, Greek pod-, pous First Known Use: before 12th century
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