This is a distorted spelling of the French words from which it is said to have originated, pied de grue.
Some of the many English forms the word has taken since its introduction into the language in the early fifteenth century, were pee de grew, petiegrew, pytagru, peti degree, pedicru, to show just a few of them.
The French phrase means “foot of a crane,” and the reason for giving this peculiar name to the genealogical table that shows one’s line of descent is explained thus:
Back in the Middle Ages, people were just as proud of their ancestry as many are today; in fact, numerous instances in the Bible, especially the First Book of Chronicles, show that such pride is very ancient. It exists among all races. But in England, the study of genealogy began to assume undue importance in the fourteenth century when, after the Norman Conquest, matters of inherited rights came into question.
Scholars, usually monks, were employed to trace back the lines of descent claimed by noblemen, or to prove that some remote relative was the legitimate heir to an estate or title after all the direct descendants had died or been killed in battle.
Hence, just as among scholars of our day certain signs or symbols have acquired particular significance, as the asterisk (*), the dagger, the double dagger, so did the genealogists of the Middle Ages also employ certain conventional significant symbols. Thus, it appears, the line of descent that one was engaged in tracing was marked by a symbol that was easy to make, a caret or inverted V having a straight line extending from slightly above the apex down through it to the base.
Some monk, probably, knowing the tracks that birds make in mud or snow, must have seen the resemblance between this symbol and the track made by a crane and, French being the court language, called it pied de grue.
The name of the mark was retained, and, marking the lines of descent, the line itself came to be called pied de grue, eventually corrupted into the English spelling, pedigree, under the influence of the French pronunciation.