What is fairwinds in the cornish language?

There isn't a single word in Cornish that translates directly to "fair winds". However, you could use phrases that convey the same sentiment:

Direct translations of parts:

* Gwythion (winds)

* Gwir (fair, true)

Phrases:

* Gwythion gwir (literally "true winds")

* Gwythion kynor (literally "winds of the north") - This phrase evokes a favorable wind direction for sailing.

More poetic options:

* Keves yn da (literally "good luck" or "good journey")

* Tregothow kynor (literally "good sailing" or "safe travels")

Ultimately, the best way to convey "fair winds" in Cornish depends on the specific context and the desired tone.