Why fear of a person who loves a child's feet covered with mud is valid, but pedopaedopedophilliacophobia is not

Sometimes the confusion between two or more similar words is merely etymological. An example of such can be the common roots for “soil”, “feet” and “child”; and the difference between pedology, pedal, and pediatrician.

The root for “soil” is derived from Ancient Greek, “ped” giving us words like pedology, or study of soil; and pedogenesis, the process of formation of soil.

For feet, the “ped” comes from Latin. Therefore the words referring to “feet” are usually made with other Latin suffixes and prefixes. Words like bipedal, tripod, millipede, pedal, pedestrian, and pedometer (or a machine for counting steps) all refer to feet. Expedite is made of “ex-“ or out, plus “ped”. So if you outpace something, you “expedite” it.  

The root word for “child” , thanks to Merriam Webster, is not child’s play anymore. In Ancient Greek, the root is spelt as “paed”. The Americans got it as “ped” and therefore we have pediatrician, instead of paediatrician; paedophile became pedophile causing confusion between earthworms and other kinds of creeps; and paedagogue became pedagogue (though no teacher ever taught that). 

So when Ted Mosby rants about “encyclopedia” being actually “encycloPAEdia”, his agitation is well directed for a book which was supposed to include “everything around the subjects a child may require” is indeed an encyclopaedia. Looking at you Merriam Webster.