Supple
Middle English: from Old French souple, from Latin supplex, supplic- ‘submissive’, from sub- ‘under’ + placere ‘propitiate’.
wiktionary
From Middle English souple, from Old French souple, soupple(“soft, lithe, yielding”), from Latin supplic-, supplex(“suppliant, submissive, kneeling”), of uncertain formation. Either from sub + plicō(“bend”) (compare complex), or from sub + plācō(“placate”). More at sub-, placate.
etymonline
supple (adj.)
c. 1300, "soft, tender," from Old French souple, sople "pliant, flexible; humble, submissive" (12c.), from Gallo-Roman *supples, from Latin supplex "submissive, humbly begging, beseeching, kneeling in entreaty, suppliant," literally "bending, kneeling down," perhaps an altered form of *supplacos "humbly pleading, appeasing," from sub "under" (see sub-) + placare "to calm, appease, quiet, soothe, assuage," causative of placere "to please" (see please, and compare supplication).
Meaning "pliant" is from late 14c.; figurative sense of "artfully obsequious, capable of adapting oneself to the wishes and opinions of others" is from c. 1600. Supple-chapped (c. 1600) was used of a flatterer. Related: Suppleness.
