"number multiplied or to be multiplied by another number," 1590s, from Latin multiplicandus "to be multiplied," gerundive of multiplicare "to multiply, increase" (see multiply).
"a number by which another number is divided," mid-15c., divisour, from Latin divisor, agent noun from dividere "to divide" (see divide (v.)).
also A1, A-one, "first-rate," 1837 (in Dickens); a figurative use from Lloyd's of London marine insurance company's system for selective rating of merchant vessels ("Register of British and Foreign Shipping"), where it is the designation for ships in first-class condition. The letter refers to the condition of the hull of the ship itself, and the number rating to the equipment. Also used in equivalent ratings in U.S., where colloquially it is sometimes expanded to A No. 1 (which is attested by 1848 as top rating of entries in an agricultural fair).