Which preposition to use with boaster

in Occurrences 4%

Ere guilty fear depress'd the hoary chief, An angry murmur, a rebellious frown, Had stretch'd the fiery boaster in the grave.

of Occurrences 3%

Going down the stairs the prince said to la Rivabarella: "Heigho! who would have thought Don Juan a mere boaster of impiety?

Which preposition to use with  boaster