John -
Could the Fillown be derived from "Phill Eoin" i.e. "the son of Philip the son of John"
I know the Cannells in Kirk Michael and the Corletts in Ballaugh were using Philip in the mid-seventeenth century, although earlier they used Finlo.
This would then resemble a name am studying in Lezayre "Bill Harry" - derived from William son of Henry, whereas other researchers who had not traced the family tree thought it was William of the Ayres or Lezayre.

Cheers, Nigel