I always thought it a bit strange that the Yani is commonly used as a short form of Yanagisawa. From an etymological point I view I might assume that Yani is used because of the often misspelt version of Yanagisawa which is Yanisigawa or some variant.
Yeah, I guess it should be Yana and Yama, but Yani and Yammy are more affectionate diminutives I s'pose. No one ever talks about a Selmy, Marty Keily or Bueschy, though, do they?
Sounds like the seven dwarfs...
Would be even funnier if they were described by the sound they make:
Honky, Snorty, Grunty, Screamy, Woofty, Farty and Gruff.