"very demanding, severe in requirement," 1580s, present-participle adjective from exact (v.).
Entries linking to exacting
exact v.
"to force or compel to be paid or yielded," mid-15c., from Latin exactus, past participle of exigere "require, enforce, demand, collect (money);" see exact (adj.). Older in English than the adjective and retaining the literal sense of the Latin source. Related: Exacted; exacting.