frightfully
UK[ˈfraɪtfəli]US[ˈfraɪtfəli]
adv
to a very great or extreme degree; very
adv
in a frightening or alarming manner
Morpheme Breakdown
fright
ful
ly
fright
fear
ful
full of
ly
adverb suffix
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
Structure: fright (fear) + ful (full of) + ly (adverb suffix)
fright (old english, meaning 'fear, dread'); ful (old english, adjectival suffix meaning 'full of'); ly (old english, adverbial suffix)
Examples
it was a frightfully expensive restaurant.
she was frightfully clever and always won the debates.
the door creaked open frightfully in the silent house.