English
keymask
From key + mask.
Proto-Indo-European *mosgʷ- ‘netting, mesh, knot, loop’
…
Proto-West Germanic *maskā ‘mesh, net’
Medieval Latin masca
Italian maschera ‘mask, disguise’
Middle French masque ‘a covering to hide or protect the face’
English mask
Today it means
noun A bitmask specifying which keypresses were made.
Language periods are conventional ranges, not dates for this word.
Etymograph / keymask