colloquial phonological shortening of naturally, jive talk, by 1945.
Entries linking to natch
naturally adv.
late 13c., "inherently, intrinsically, characteristically," from natural (adj.) + -ly (2). From late 14c. as "in accord with natural law;" also "normally; usually, expectedly; as a matter of course, consequently, understandably." The notion is "as a natural result." From early 15c. as "without artificial assistance, by a natural process."