C90 Controller described a near loss of separation event when traffic was issued direct ACITO but programed ACETO for the turn; the reporter suggesting renaming the lessor used ACETO fix.

Narrative

Aircraft X departed Runway 22 (L/R?) off MDW. The only competing traffic was an arrival far to the west descending to 5;000 and would have been a non-factor. I issued a climb to 120 and direct ACITO. A short time later I notice the aircraft taking a fairly drastic turn to the southeast in his climb; well away from ACITO. We asked to verify where he was turning and to spell the waypoint; to which he replied ACETO. While it was never close; his turn definitely took him more in to the path of the arrival than intended. I had him climb through 6;000 without delay and got him back on course to ACITO. Recommendation; it appears ACETO waypoint is the FAF for the RNAV (GPS) Runway 6 approach at FFT airport. The aircraft; per the strip; was issued an FRC to CPS. Assuming it was a verbal clearance; confirm the spelling of ACITO since it's a fairly critical initial departure fix. This would be very time consuming in the long run however; and only bandaids the issue. Probably more efficient and safe as a permanent fix would be to rename (and possibly retire) the ACETO way point at FFT since 1.) Its spelling is close; 2.) Pronunciation can be similar (especially since the pronunciation of ACITO is defined in the C90 SOP); and 3.) ACITO must be a much-more-heavily used fix since it apples to numerous Chicago Metro Area departures on a daily basis.