Err… no spoilers, but one character in Terry Pratchet’s Night Watch uses his homemade dog Latin. Anyone have a “translation” of these phrases:
Ave! Duci Novo, similis duci seneca!
and
Ave! Bossa Nova, similis bossa seneca!
The translation they give in the text is "Meet the new boss, same as the old boss, but I wanted to hear what Pterry actually did with the language. He has a repuation for… creative grammer.
I think the second one might be “Blame it on the bossa nova, the dance of love.” 
I could have guessed from the literal translations and the context that he was trying to quote the Who’s “Won’t Get Fooled Again.” He just uses some odd cases and choices of words.
“Ave” is a greeting, meaning “hail.” I don’t see how it fits here.
Dux means “leader” and novus means “new.” Since the words seem to be in the dative case, I guess it means “Hail to the new leader (boss).”
Similis means “similar to.”
“Bossa” certainly doesn’t mean “boss” or, to my knowledge, anything else in Latin. I suppose the writer is just being a wise guy. “Seneca” does mean “old” but not in the sense of “previous” or “former.” It means “old” as in “ancient” or “elderly.”
So, literally, it means something like, “Greetings, new leader (boss),” similar to the elderly ___."
I see, said the bandit.
Pterry doesn’t use pig or dog Latin. He just invents or distorts words, mix with some Latin from aphorisms and presto - it seems to be Latin, but it ain’t.
‘Fabricate Diem Pvnc’, being the prime example.
The quotes in the OP are, I suppose, meant to mean the same.
It should be noted that “Meet the new boss, same as the old boss” is a line from The Who song, “We Won’t Get Fooled Again.” The song also figures in the battle cry of the Nac Mac Feegle in The Wee Free Men.