The word is " _comon_ ", and was used here as an abbreviation of the word " _commission_ ". The phrase:
> "... to whom administration was granted having been sworn by commission duly to administer."
being a standard one in wills of that period.
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This not an unusual abbreviation in this context, although personally I have found the simpler " _com_ " or " _comm_ " to be more often used for " _commission_ ".
Similarly, (as you noted in your transcript) " _admon_ " is used as an abbreviation for " _administration_ " earlier in that paragraph.