The phrase "snakes in the boot" is an idiom that refers to an unexpected and unwelcome surprise. Synonyms for this expression include "a thorn in one's side," "a monkey wrench in the works," or "a curveball." These idioms are used to describe something that disrupts the normal course of events, causing difficulty or inconvenience. They can also refer to a hidden or unexpected threat, much like the snakes in the boot. Other synonyms for this phrase may include "a spanner in the works," "a fly in the ointment," or "a bump in the road." All of these expressions convey a sense of disruption and inconvenience, much like the unexpected appearance of snakes in one's footwear.