To hollow out or form into a case; to encase or place within a protective covering.
From 'case' (from Old French 'casse') plus the verb-forming suffix '-ate', which creates verbs meaning to make or treat with.
This word is almost extinct in modern English, but it survives in metallurgy where 'case-hardening' involves casating steel with carbon!
Complete word intelligence in one call. Free tier — 50 lookups/day.