You could select one instance of "aye aye" and apply a custom character style with the language setting checked for "do not check spelling or grammar." Then do a replace for "aye aye" replacing it with "aye aye" with your no-proofing character style applied.

I would save the style to your template for future use.

You should note that such a style or actually the setting itself, is sticky. If you copy text with it and change the text, it will, invisibly, continue to be exempt from spell checks until the style (no-proofing formatting) is removed from the text.