The word is fine; I learned first from reading Patrick O’Brian’s marvelous novels. What really gets under my skin is that the OED is citing Twitter for usage. Okay, it’s the internet era, but Twitter? Really? We’re all on a bobsled to Gehenna, friends.
ahoo, adv. and adj.
†1. Unjustly, wrongfully; in error. Cf. mid or with wough at WOUGH n.2 2c. Obs.
2. Askew, awry; crookedly, lopsidedly. Chiefly in all ahoo. Cf. HUH n. regional in later use.
Chiefly Naut. and regional. In predicative use: crooked, lopsided; askew, awry; disordered. Chiefly in all ahoo.
2015 @AMinorMuddle 10 May in twitter.com (O.E.D. Archive) A somewhat muddly time being had. Decorators due tomorrow. House all ahoo.