To make silly, foolish, or dazed; to stupefy or confuse someone.
From 'be-' prefix plus 'daff' (from Middle English, possibly related to 'daft' meaning silly or foolish). The prefix 'be-' here creates a verb meaning to render someone foolish or senseless.
This is one of the most obscure 'be-' verbs, appearing rarely even in historical texts—it seems people preferred just saying someone was 'daft' rather than using the verb form 'to bedaff them.' Some words just never catch on, even when they're formed according to perfectly normal English patterns!
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