B737 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 200; Flight Crew Type 8000
Communication Breakdown
ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Provided Assistance; Flight Crew Became Reoriented
Human Factors
Reaching cruise altitude; ZSE cleared flight to WINEN waypoint. We then commented on how the Controller pronounced the waypoint wrong as we thought his intention was to clear the flight to WYYNN waypoint due to early hours. Soon after; we received short vector for traffic. ZSE then re-cleared us to WINEN and we re-entered WYYNN and read back the pronunciation for WYYNN waypoint. In retrospect; the Controller pronounced his intended waypoint correctly; but I replied with his pronunciation the first time even though I thought he was incorrect in pronunciation. My understanding; at the time; was the Controller was clearing the flight to WYYNN and pronouncing it as WYNN-N. Several minutes later; the Controller queried us as he showed us off course. We replied we were previously cleared direct WYYNN and doing the same. He then advised us that we were now cleared to WINEN as filed. He went on to say that this occurs 'all the time' and they were trying to 'get it fixed.' The flight proceeded as filed and landed uneventfully.
B737 Captain reported navigating to wrong waypoint WYYNN instead of WINEN due to communication issue with ATC and fix name similarity.