1788, colloquially, originally of horses, by 1801 of persons, "having the toes curled in;" see pigeon. Of birds, "having the foot structure which characterizes the pigeon," by 1890.
pig
pig iron
pig Latin
pigeon
pigeon-hole
pigeon-toed
pigeon-wing
piggish
Piggly-Wiggly
piggy
piggyback