Aquatic Biology

I've been studying (still should be, but gimme a while) for my aquatic biology test tomorrow and I've come to remember all these funny names that people give living creatures to insult them

Here're some examples. There're birds that are called 'boobies' and another species called 'tits', not to forget a species by the name of "shags". These are common names though, not the Latin names using the Linnaeus system (e.g. Homo sapiens). Also, there are "Priapulan worms" that are named after some Greek penis God, which translates literally, to "penis worms".

I don't get how those birds got named that way, but for the Penis worms..

I guess they do have a point, don't they?