Of, relating to, or of the nature of a cryptogram; written in or using secret codes or hidden meanings.
An extended adjectival form of 'cryptogram' using the '-ical' suffix, this variant emerged in scholarly texts to provide more formal or emphatic expression of the concept of hidden or encoded writing.
The distinction between '-atic' and '-ical' endings is subtle but real—'cryptogrammatical' sounds more formal and scholarly, the kind of word you'd find in a linguistics paper rather than casual conversation.
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