Man pages matching name itkvars in section 3itk:

itkvars.3itk.en	debian 10 / itk3-doc
itkvars.3itk.en	debian 10 / tk-itk4-doc
itkvars.3itk.en	debian 11 / itk3-doc
itkvars.3itk.en	debian 11 / tk-itk4-doc
itkvars.3itk.en	debian 12 / itk3-doc
itkvars.3itk.en	debian 12 / tk-itk4-doc