early 13c., "visible form or appearance of a person," from Old French figure (10c.) "shape, body, form, figure; symbol, allegory," from Latin figura "a shape, form, figure," from PIE *dheigh- "to form, build" (see dough); originally in English with meaning "numeral," but sense of "form, likeness" is almost as old (mid-13c.).
Philosophical and scientific senses are from Latin figura being used to translate Greek skhema. The rhetorical use of figure dates to late 14c.; hence figure of speech (1824). Figure eight as a shape was originally figure of eight (c.1600).