Ped-

The prefix ped- (usually in the combining forms peda-, pedi-, and pedo-) in English and various other Western languages has multiple Latin and Ancient Greek roots, and multiple meanings. Ped- (sometimes spelled paed-, pæd-, or rarely paid-, depending on the word and the language or dialect) is a prefix in English and many other Western languages, often with divergent spellings, such as "pet-", "pie-", "pei-", etc. 
Meanings.
Ped- conveys multiple meanings, from different Latin and Ancient Greek root words:
In meanings 2, 3, and 4, the spelling remains "ped-" in Commonwealth English words that begin with these letters. Not all derived words do; e.g., "petard" (a small bomb) is from meaning 4, and entered English from Middle French for the same thing (originally literally meaning 'fart', it remains an uncommon Modern French word for 'firecracker').
Relating to children.
Commonly in English, it is from the Greek (), originally meaning 'boy'. as well as 'child'. Contemporarily, it is more associated with the word 'child'. Words derived from this particular root are spelled "paed-" most cases in Commonwealth English varieties (formerly with a ligature, "pæd-"). 
Relating to feet.
Meanings related to feet are from Latin (, 'foot'):
A Greek-derived
 equivalent, "pod-", is often employed instead, as in "podiatry". The Greek-based "-pus" suffix conveys the same meaning, as in "octopus".
Relating to soil or plains.
Ped- can also refer to soil. This prefix is from Greek (, 'soil', 'the ground')
The derived Greek word and (, 'field or plain')
Relating to flatulence.
Another meaning, relating to flatulence, is from Latin (infinitive , 'to fart'). It does not appear in English except in loan words but is the root for words referring to flatulation in several Western languages, often in modified form such as "pet-"
Other uses.
It may also be used as an infix: such as with encyclopedia (encyclopaedia), and orthopedics (orthopaedics).
Some common English words with this derivation include: