Whence (and from whence) and whilts are very uncommon in US speach and writing.

i used to have UK produced instruction manuals that suggested Whilst holding with a spanner...

these direction alway were fun.. Our staff was such a mixed bag-- about 25% understood (from UK, or Jamaca, or other island that has british based schooling.) but many of the other nationals (pick a country!) who's first language was not english, really had a problem.