Pettifog \PET-ee-fog\ , verb;
1. To bicker or quibble over trifles or unimportant matters
2. To carry on a petty, shifty, or unethical law business
3. To practice chicanery of any sort
Pettifog and pettifogging both come from pettifogger, which dates to the 1560's and is based on petty and a second element possibly from Dutch focker. Focker comes from either Flemish focken ("to cheat") or Middle English fugger, which is the surname of a renowned family of merchants and financiers in Augsburg, Germany in the 15th and 16th centuries. From that famous family, the word came to mean "monopolist, rich man, usurer."
Petty dates to the late 14th century as "small" from Old French petit ("small"), which probably derives from Late Latin pitinnus ("small") of unknown origin. The original meaning in English was not negative, which survives in the term petty cash. By the 1520's it had come to mean "of small importance" and evolved into "small-minded" by the 1580's.