“sent with broom before, / To sweep the dust behind the door”
Sweeping the house before a fairy procession was a standard piece of English folklore associated with Robin Goodfellow (Puck's folk name). The broom cleared away evil spirits or household dirt to ready the space for the fairies' blessing.
historical Robin Goodfellow“Never mole, hare-lip, nor scar, / Nor mark prodigious”
'Prodigious' here means ominous or monstrous (not merely large). Elizabethans interpreted visible birth defects as signs from nature — a 'prodigious mark' warned of ill fortune or divine displeasure. The fairy blessing inverts this anxiety: these children will bear no such mark.
“field-dew consecrate”
Oberon uses field-dew (morning dew gathered from grass) as a ritual sprinkling agent. 'Consecrate' = made holy. The image echoes Catholic holy-water blessing of houses and beds — a ritual familiar to Elizabethan audiences from pre-Reformation England, here transferred to fairy magic.
“weak and idle theme, / No more yielding but a dream”
Puck recasts the play as a trivial dream, using the standard Elizabethan epilogue move of mock-apology. 'Idle' = worthless, of no substance (OED s.v. idle adj. 4). 'No more yielding but a dream' = producing nothing more than a dream — the play-as-dream conceit that runs through the whole work.
“serpent's tongue”
The serpent's tongue = the hissing sound an Elizabethan theatre audience made to express displeasure, equivalent to modern booing. Puck hopes to 'escape' it — to avoid having the play hissed off the stage.
“Give me your hands, if we be friends, / And Robin shall restore amends”
'Give me your hands' = applaud (clapping hands together). This is the standard epilogue call for applause, corresponding to the Latin stage convention 'plaudite manibus' (clap with your hands). 'Robin' is Puck's folk name — Robin Goodfellow — used here to close the epilogue on a domestic, familiar note.
historical Robin Goodfellow