Your father's mustache!

[chasmala]

My daughter asked me where the phrase "You father's mustache!" comes from since I say it all the time when I do something stupid. I have no idea where I got this saying nor what it really means.

[Thunderchild]

well not in answer to your question but here in italy when someone does something stupid they say your sister to them or rather when someone sais something stupid. so i think your fasthers mustache is a much better alternative

[Octavius]

Apparently the phrase dates back to the 1920's in the US, but there is little written on the origin.  My flurry with google pointed to either of the following:

• a chain of barber shops called YFM who suffered from bad business practices and were eventualy taken over by the Regis Corporation, or.....
• a popular jazz/dixie band (and subsequent nightclub chain) who used to play lively and sometimes daft sporadic improvised music.

Your guess is a good as mine.

[Kingaroo]

I think one can swear a vow in the name of various boyd parts of ones self or loved ones. You can swear by your mother's head, for example, meaning that if you lie, your mother will be decapitated. Swearing by hairs might imply that you were unwilling to take even the smallest, least threatening risk. The three little pigs swore "not by the hair on my chinny-chin-chin." I think "by my father's mustache" must be a whimsical variation and probably predated the barbarship and music group that Octavius refers to.

Caveat: this is all off the top of my head (where the hairs are!) and unsubstantiated by research.