Pulpo (Spanish for octopus)
Antonio, after Antonio Alfonseca, the six-fingered baseball pitcher nicknamed El Pulpo.
I see that njtt beat me to Paul, the psychic German octopus that predicted World Cup results in 2010
Beaker, because octopuses have beaks.
Lefty
Liam Neeson
<longexplanation>My daughter Arwen received a plush octopus and decided to call him after the actor. She was also taking Spanish 1 at the time and thus begged the knowledge of how to say, “My octopus is called Liam Neeson.” Another of my daughters, Juliet, began dating a young man whose mother spoke only Spanish. When the mom and Arwen were seated next to each other at a get-to-know-you lunch, Arwen turned to her and blurted out, in perfect Spanish, “Mi pulpo se llama Liam Neeson!” I don’t believe the poor woman ever recovered. 
</longexplanation>
StG
Awesome suggestions, everybody. Thanks so much!
Grrlbrarian, are they still together? (Arwen & Liam, of course.)
Horatio has a marine feel to it. (From the Horatio Hornblower books)
Call him The Eight-Fold Way.
From Buddhism: A Basic Buddhism Guide: The Eight-Fold Path
From physics: Eightfold way (physics) - Wikipedia
The Spider-Man references are overdone.
Huggly
Tentacles (rhymes with Hercules)
Riley,R’lyeh
For some subterfuge go with Maud because of Octopussy (1983) especially if you can dress it up to look like any of these.
Inkubus
Octane
Joe
Incubus
If you’re not nice to him, he will ink u bus.
(Yeah, I know)
Otto.
A Fish Called Wanda:
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Are you really Italian?
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Absolutamente. Sì.
My name is Otto. It means eight.
Little Cthulu. Bonus points for punning on “Little Lulu.”
Yes, singular1, they are. We all adore cephalopods! 
Get him one of these and call him Damphair.