chink in one's armor, a

chink in one's armor

A vulnerable area, as in Putting things off to the last minute is the chink in Pat's armor and is bound to get her in trouble one day . This term relies on chink in the sense of "a crack or gap," a meaning dating from about 1400 and used figuratively since the mid-1600s.
See also: armor, chink

chink in one's armor, a

A vulnerable spot, a weakness. The term alludes to the medieval knight’s armor made of mail—interlinked rings of metal jointed at various points. When a crack, or chink, developed between the links or joints, he was less protected against a spear or arrow. The noun “chink” has been used figuratively for such a fissure since the 1600s, and the current term came soon afterward. See also Achilles' heel.
See also: chink