Which preposition to use with executrix

of Occurrences 314%

"I nominate and appoint Roswell Gardiner, now absent on a sealing voyage, in my employment, as the sole executor of this my last will, provided he return home within six months of my decease; and should he not return home within the said six months, then I appoint my above-mentioned niece and heiress, Mary Pratt, the sole executrix of this my will.

for Occurrences 4%

ZADORY, AURELIA, executrix for the Estate of Helen Wells.

Which preposition to use with  executrix