frightfully
Meaning
to a very great or extreme degree; very
in a frightening or alarming manner
Structure
Usage
it was a frightfully expensive restaurant.
she was frightfully clever and always won the debates.
the door creaked open frightfully in the silent house.
Etymology
The word 'frightfully' is built upon the Old English noun 'fryhto' or 'fyrhto', meaning 'fear' or 'dread'. The adjectival suffix '-ful' was added to form 'frightful', literally meaning 'full of fear' and thus 'causing fear'. The final adverbial suffix '-ly', also from Old English, converts the adjective into an adverb. The modern intensive sense of 'extremely' developed in the 18th and 19th centuries through hyperbole, where something so extreme as to be frightening came to simply mean 'very'.
Analysis
fright (old english, meaning 'fear, dread'); ful (old english, adjectival suffix meaning 'full of'); ly (old english, adverbial suffix)