Also in the UK and never heard of this in my life. Guessing this is very regional?
I used to think everyone called (cobs|bread cakes|rolls|barns) muffins, and it turns out it was just my small town that did it. As in, just my small town, not region, county, etc.
I ask because i'm only familiar with a thread/yarn bobbin, I wonder if it derived from that.
UK regional dialects are summed up really well here because despite listing five different names for a specific thing you still neglected the word I use (baps).
(So obviously those calling them cobs or rolls or whatever else are just wrong!)
[0] https://www.oed.com/dictionary/barm_n2?tab=meaning_and_use#2...