active word-forming element in English and in many verbs inherited from French and Latin, from Latin de "down, down from, from, off; concerning" (see de), also used as a prefix in Latin, usually meaning "down, off, away, from among, down from," but also "down to the bottom, totally" hence "completely" (intensive or completive), which is its sense in many English words.
As a Latin prefix it also had the function of undoing or reversing a verb's action, and hence it came to be used as a pure privative — "not, do the opposite of, undo" — which is its primary function as a living prefix in English, as in defrost (1895), defuse (1943), de-escalate (1964), etc. In some cases, a reduced form of dis-.
c. 1200, trone, "the seat of God or a saint in heaven;" c. 1300 as "seat occupied by a sovereign," from Old French trone (12c., Modern French trône), from Latin thronus, from Greek thronos "elevated seat, chair, throne," from suffixed form of PIE root *dher- "to hold firmly, support" (source also of Latin firmus "firm, steadfast, strong, stable," Sanskrit dharma "statute, law"). From late 14c. as a symbol of royal power. Colloquial meaning "toilet" is recorded from 1922. The classical -h- begins to appear in English from late 14c.