In the manner of an apothegm; in a way that is pithy, concise, memorable, and expressing wisdom briefly.
From apothegmatical plus the adverb-forming suffix -ly. This creates the adverbial form to describe how an action is performed in an apothegm-like manner.
Adding -ly to apothegmatical creates this wonderfully unwieldy word—it's almost too long to be pithy itself, which is a delicious irony when you're using it to describe something that's supposed to be brief and punchy!
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