Is it ensure, insure, or assure?
in ballet, 1892, from French plié, from plier literally "to bend," from Old French ploier (see ply (n.)).
"work with, use," late 14c., shortened form of applien "join to, apply" (see apply). The core of this is Latin plicare "to lay, fold, twist," from PIE root *plek- "to plait, twist" (cf. Greek plekein "to plait, twine," plektos "twisted;" Latin plectere (past participle plexus) "to plait, braid, intertwine;" Old Church Slavonic plesti "to braid, plait, twist;" Gothic flahta "braid;" Old English fleax "cloth made with flax, linen").
Sense of "travel regularly" is first 1803, perhaps from earlier sense "steer a course" (1550s). Related: Plied; plies; plying.
"to bend," late 14c., plien, from Old French plier, earlier pleier "to fold, bend," from Latin plicare "to lay, fold, twist" (see ply (v.1)). Related: Plied; plies; plying.
(French: "bent"), knee bend in ballet. It is used in jumps and turns to provide spring, absorb shock, and as an exercise to loosen muscles and to develop balance. Performed in all of the five basic foot positions, plies may be shallow, so that the dancer's heels remain on the floor (demi-plie), or deep, so that in all foot positions except the second the heels rise (grand plie).