Playful joking or fooling around; acting silly or making jokes.
From the verb 'daff' (to joke or act foolishly) + present participle suffix '-ing'. The verb 'daff' is primarily British dialect.
This is a beautiful example of British English holding onto words that are fading elsewhere—'daffing about' is still common in UK speech for 'messing around,' preserving a lively medieval verb that most English speakers have forgotten.
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