I collect (horde?) vintage machines, so when possible I name them after their original owner. Sometimes I get the name from the seller, other times I find it written in a manual or on some service documents that came with the machine.
A few don't have names yet for whatever reason, I call them things like "sweetie" or "little girl" when I'm trying to coax them into working. ("Little Girl" is also what I call my car.)
The ones with names:
Modern machines:
90's Kenmore - "Stitch" (this was the first machine I bought after moving out of my parent's home, I abused this poor machine SO MUCH and yet he still keeps working...such a trooper!)
Janome 6600 - "Princess Leia" - my dealer gave her this name and I thought it was funny so I kept it.
Janome 3160 - "Chewbacca" - since I already had a Star Wars theme going...
Vintage horde:
Kenmore 117-959 - "Judy", after my boss's mom (he helped me get the machine & cabinet home)
Kenmore 158-1651 - "Hulk", because it's made of steel and anger, and is slightly green
Singer 319W - "Verne" - it's sort of steampunky looking with those levers, so named after Jules Verne
Singer 221 - "Patricia" - after original owner
Singer 185K - "Kathy" - after original owner
White 1563 - "Betty", because I love Betty White
Singer 99K - "Darling", because it's so cute! I have two, one is older than the other, so they're actually "Darling the younger" and "Darling the elder"
Singer 128 - "Venny", because of the La Vencedora decals (not very imaginative)
Singer 403A - my newest acquisition, I've decided she's a "Lucille"
Singer 500A - my Rocketeer just is called "The Rocket"
The rest will get names as they come to me. Sometimes I have a name right away, other times I have to get to know the machine before they tell me what to call them. Some machines I decide are male, some are definitely female....it's all a little arbitrary and silly, but I have fun with it!