early 15c., commentacioun, "act or practice of writing commentary, annotation," from Latin commentationem (nominative commentatio), noun of action from past-participle stem of commentari "consider thoroughly, think over, discuss, write upon," from commentum "comment, interpretation" (see comment (n.)). From 1833 as "the making of comments."
commensurable
commensurate
comment
commentary
commentate
commentation
commentator
commenter
commerce
commercial
commercialism