Properly, "recitativo arioso," this is, a recitative of a lyrical and expressive quality, not, as usual, narrative and speechlike.  The arioso style, therefore, is midway between that of a recitative and an aria.  Historically, the arioso came earlier than the speech-like recitative.  All the composers of the Florentine opera (Peri, Caccini, Monteverdi) employed the "recitativo arioso," the expressive and quasimelodic recitativeBach often uses the arioso for the concluding section of a recitative in order to give it a particular expression of assurance or confidence.