trick of the trade, A clever or expert way of doing something, often known only to those in a particular profession.
up to one's old tricks, Engaging in the same deceitful or mischievous behavior as before.
Word Origin
Language
Old French
Original word
trichier
Originally meant
to deceive or cheat
Background
The word 'trick' comes from the Old French 'trichier', which means to deceive or cheat. It entered the English language in the late Middle Ages, reflecting the influence of French on English vocabulary after the Norman Conquest.