Flexible started as a purely physical description — something that bends without snapping. Latin flectere meant 'to bend or curve,' and flexibilis was its adjectival form: 'that which may be bent.' Old French borrowed it as flexible, and English adopted it in the early 1400s. For the first century of its English life, the word described only materials: flexible branches, flexible metal, flexible limbs. The figurative leap — a flexible mind, a flexible schedule — appeared by the sixteenth century as writers recognised the metaphorical power of bending without breaking. Today the figurative sense dominates everyday usage. The Latin parent verb flectere generated one of English's most productive word families: deflect (bend away), reflect (bend back), inflect (bend inward), and genuflect (bend the knee). The deeper origin of flectere remains debated, though some linguists trace it to a Proto-Indo-European root meaning 'to bend,' possibly related to the ancestor of the English word 'black' through the concept of burnt, curled material.