If it helps, it's not actually -son in
Alison. It's composed of
Alis- (i.e.
Alice) and -on (a medieval French diminutive suffix). You see the same ending in names like
Manon,
Marion, and
Ninon.
https://nanowrimo.org/participants/christine-seaforth-finch
http://christineseaforthfinch.blogspot.com/