grin and bear it suffer pain or misfortune in a stoical manner.

☞ The usual modern sense of grin is less sinister than its earliest senses: when it entered the language it primarily meant 'an act of showing the teeth' or 'a snarl'. From the mid 17th century to the mid 18th century, a grin was generally used in a derogatory way or in unfavourable contrast to a cheerful smile. The sense of grin in grin and bear it retains the earlier associations with showing your teeth in a grimace of pain or anger. Grin and abide is recorded as a proverb in the late 18th century; the modern version dates from the late 19th century.