c. 1200, trone , "the seat of God or a saint in heaven;" c. 1300, "seat occupied by a sovereign, potentate, or dignity on earth," from Old French trone (12c., Modern French trone ), from Latin thronus (Medieval Latin tronus ), from Greek thronos "elevated seat, chair, throne," according to Watkins from suffixed form of PIE root *dher- "to hold firmly, support" (source also of Latin firmus "firm, steadfast, strong, stable," Sanskrit dharma "statute, law").

Attested from late 14c. figuratively as a symbol of royal power. The colloquial meaning "toilet" is by 1960; comparison of the toilet to a throne is by 1922. The classical -h- begins to appear in English from late 14c. Related: Thronal .

word-forming element meaning "in; into," from French and Old French en- , from Latin in- "in, into" (from PIE root *en "in"). Typically assimilated before -p- , -b- , -m- , -l- , and -r- . Latin in- became en- in French, Spanish, Portuguese, but remained in- in Italian.

Also used with native and imported elements to form verbs from nouns and adjectives, with a sense "put in or on" ( encircle ), also "cause to be, make into" ( endear ), and used as an intensive ( enclose ). Spelling variants in French that were brought over into Middle English account for parallels such as ensure / insure , and most en- words in English had at one time or another a variant in in- , and vice versa.