c. 1300, devis, "intent, desire; an expressed intent or desire; a plan or design; a literary composition," from Old French devis "division, separation; disposition, wish, desire; coat of arms, emblem; a bequest in a will, act of bequeathing," from deviser "arrange, plan, contrive," literally "dispose in portions," from Vulgar Latin *divisare, frequentative of Latin dividere "to divide" (see divide (v.)).
The basic sense is "method by which something is divided," which arose in Old French and led to the range of modern meanings via the notion of "something invented or fitted to a particular use or purpose," hence "an invention; a constructed tool; inventiveness; a contriving, a plan or scheme."
In English from c. 1400 as "artistic design, work of art; ornament," hence especially "a representation of some object or scene, accompanied by a motto or legend, used as an expression of the bearer's aspirations or principles." Also from c. 1400 as "mechanical contrivance," such as a large crossbow fitted with a crank. From mid-15c. as "a bequest in a will." Since c. 1996 the word has come to be used especially for "hand-held or mobile computing or electronic instrument."