Parallel translation:

設計沖波の見直しとその手法に関する福島県の事例について
Case Study of Fukushima with Regard to the Review of Design Offshore Waves and its Method 
http://www.jific.or.jp/dispatch/ronbun/pdf_r30/3005.pdf

https://en.wikipedia.org/wiki/Japanese_destroyer_Okinami
Okinami (沖波, "High Seas Waves") was a Yūgumo-class destroyer of the Imperial Japanese Navy.

https://eow.alc.co.jp/search?q=沖波
沖波
offshore wave

offing: "the part of the deep sea seen from the shore"
https://en.wikipedia.org/wiki/Horizon
On Earth, when looking at a sea from a shore, the part of the sea closest to the horizon is called the offing.[1]

We already removed "offing" from 沖合, where it might have been appropriate(eijiro knows about it, but glosses extensively as "offshore").

I think we're better off without it here as well.

Technical texts in google book results that use "offing wave" seem to invariably have Japanese authors, suggesting that they might have relied on this vary gloss.  

The concept doesn't really make sense.  What is a wave "where the ocean meets the horizon". 

There is an English book called "Waves of the Sea and Other Water Waves", but the collocation is an accident:
"When, on the other hand, the wind is offshore, with a rough see in the offing, waves do not break until they come quite close to the beach."

@@ -15 +15 @@
-<gloss>offing wave</gloss>
+<gloss>offshore wave</gloss>

koj, daijr