You’re such an old fuddy-duddy!fuddy-duddyfud‧dy-dud‧dy /ˈfʌdi ˌdʌdi/ noun (plural fuddy-duddies) [countable] 
You’re such an old fuddy-duddy!—fuddy-duddy adjective
WORD ORIGINfuddy-duddy
Origin:
1900-2000 Perhaps from fussy + dad or dudEXAMPLES FROM OTHER DICTIONARIES
- That dress makes you look like such a fuddy-duddy.
- I know I sound like some fuddy-duddy here.
- No doubt you will merely accuse me of being an old fuddy-duddy trying to stop young people having fun.
COLLOCATIONS FROM THE ENTRY You’re such an old fuddy-duddy!
someone who has old-fashioned ideas and attitudes: You’re such an old fuddy-duddy! You’re such an old fuddy-duddy!—fuddy-duddy adjective