Origin: 1250–1300;Middle Englishdite < Anglo-French,Old Frenchdit(i)e poem, noun use of past participle of ditier to compose < Latindictāre; see dictate
c.1300, from O.Fr. ditie "composition, poem, treatise," from L. dictatum "thing dictated," neut. pp. of dictare "dictate." Ditty bag is 1850s nautical slang, perhaps from Brit. naval phrase commodity bag.