NY / NJ in the 60s, never heard of it.
Wow. Simply… wow. Thanks, everybody.
Saskatchewan, 70’s, everyday playground terminology, but not “underdog”, “underduck”. My daughter (Saskatchewan, 2000’s) will often demand the same thing in the same terms.
NE Ohio in the 80’s: it was a pretty common manuever.
Grew up in 70’s and 80’s, Virginia. Never heard of it, sounds like a term for being lazy or doing something in an understated way.
Montana, early 80’s, yes.
NE Ohio in the 50s. Never heard of it.
Underduck, in the 80’s in Alberta.
Give “a buck” on my bike! Yes! My (southern) husband thought I was crazy! Im from MSP. But we both called running under the swing an “underdog”.
Likewise in the 1980s.
Giving someone a ride on your bike was called “doubling”, I think. But an Australian friend of ours referred to that as “dinking”, which sounds much funnier to me.
Someone please tell me why Zombie threads get resuscitated?
Rockland/Orange county NY, 1980’s, and yup, that’s what it’s called. I was always too chicken to do it myself.
The board is indexed by Google, threads are found, dates not noticed(or cared about), zombie lurches forth.
Born in 1986, Southern Oregon. I didn’t know it off the top of my head but now that you’ve reminded me, yup, that’s underdogging.
I’m 52 now, grew up in extreme western Ohio. I was an expert at giving an underdog, because I was taller than average. I’m too slow do be able to do it well now 
- TBTB don’t give a crap!
I vaguely remember it, after seeing it defined. So did my sister, so I know it wasn’t just deja vu or from having seen this thread four years ago.
Just think of it as SDMBclassic. All the threads you missed, a few at a time.
Grew up in the 60’s in Edmonton and I knew it as “doing an underduck”
Chicago in the 50s and I am familiar with it.