From The Collaborative International Dictionary of English v.0.48:
-ize \-ize\suff. [F. -iser, L. -izare, Gr. ?.]
A verb suffix signifying to make, to do, to practice; as,
apologize, baptize, theorize, tyrannize.
[1913 Webster]
Note: In the case of certain words the spelling with -ise
(after analogy with F. -iser) is the usual form; as,
catechise, criticise. With regard to most words,
however, which have this suffix there is a diversity of
usage, some authorities spelling -ise, others (as in
this book) -ize.
[1913 Webster]