Where do any common names come from?
Interesting question though because as you stated they are about as aggresive as daisy, and certainly don't look like any pitbull i have seen.
With plecos some of the common names make sense straight away, e.g.
zebra pleco
green phantom
bristlenose etc
but some make no sense at all, weird aint i?!?! :?
i mean where the heck did they get Shampupa Pleco from?? always makes me laugh that one