I looked up attercop, and it says one of the meanings is 'spider,' so that's kind of obvious. Also, FYI, the modern Norwegian for spider is edderkopp.
Lazy Lob you can look up for yourself as the full meaning (which is slang and would be offensive if you called anyone by it) is not family-friendly at all. However, lob alone is taken from Old/Middle English word meaning 'spider.' Same deal with cob.
Tomnoddy was apparently an offensive term for a foolish or stupid person.
I think it's obvious why Bilbo used those names once you find their meanings...I can imagine the spiders would be very offended, being called lazy and crazy and foolish and an unwholesome slang term.
not quite Eonwe, the meaning wasn't spider for all Attercop literally means 'poison-head', and was actually a word used for a variety of poisonous creatures - from atter, we also derive our modern word adder, a type of poisonous snake. Cob is probably a shortened version of attercop, and survives to modern times in the word cobweb. Lob most famously appears in Shelob, and lob is as Eonwe said a word for spider.
As for the rest they have been explained but 'Tomnoddy' is an old fasioned British word used for mild offence. For example: 'Who's that Tomnoddy?' if you are refering to some odd stranger in the street.
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