Flex etymology in English

Etymology Blog

English word flex comes from Latin flecto, Latin flectere

Dictionary entry	Language	Definition
flecto	Latin (lat)	(figuratively) I persuade, prevail upon, or soften. I bend, curve or bow. I turn or curl.
flectere	Latin (lat)
flexus	Latin (lat)	(grammar) inflection. (of speech) modulation, inflection of the voice. A bending, turning, winding. A transition, changing.
flex	English (en)	To bend something.. To move part of the body using one's muscles.. To repeatedly bend one of one's joints.. To tighten the muscles for display of size or strength. (countable) The act of flexing.. (countable, geometry) A point of inflection.. (uncountable) Flexibility, pliancy.. (uncountable, chiefly, British) Any flexible insulated electrical wiring.

Flex etymology