Two Letter Boy Names

Were boys really named Wm at the turn of the last century, or was the old-timey abbreviation of William simply what was noted on the official records? We're guessing the latter, but as the Social Security Administration counts each spelling of a name in its tally and doesn't presume to change Wm into William (or Bryleigh into Briley, or is it Brylee?), this name stands as is through the ages.