1604, in fig. phrase
seamy side "least pleasant, worst," from
seam (q.v.), the
seamy side of a sewn garment being the less attractive, and thus typically turned in. The popularity of the fig. sense likely is due to its use by Shakespeare in "Othello" IV.ii.146: "Some such Squire he was That turn'd your wits the seamy-side without, And made you to suspect me with the Moore."