We choose names for our kids after people we want them to aspire to be like, people who model a certain trait very well. Sort of like how the puritan would name their children virtues to remind them to be like that. We just learned the story of Telemachus and his efforts in ending the gladiator battles and wow! This could be the boys name we’ve been looking for (We’re not expecting a boy at the moment. We just like to have a good name for each gender sitting on the shelf 
). Except that Telemachus is completely unusable. And we can’t figure out any way to adapt it to make it work. Can we please get some help on figuring out how to use the name Telemachus?
I’m not exactly sure if you’re looking for another FN to use, or some nn’s, but I can only think of a few for the latter:
[name_m]Mac[/name_m]/[name_m]Mack[/name_m]
[name_u]Tal[/name_u]
[name_u]Charlie[/name_u] (??? - possibly, from the ‘ch’ in the name)
Another way to use it could possibly using Telemachus as a FN, but calling the child by his middle name, as many people do with aged or “unusable” names that are still important namesakes.
You could always follow the time-honored naming tradition of putting it in the middle. Otherwise, why don’t you use [name_m]Homer[/name_m], since Telemachus appeared in [name_m]Homer[/name_m]'s Odyssey? Odyssey would make an intriguing, if bold choice, and would work especially well as a middle name.
You may also want to consider names that have the same meaning as Telemachus, or names that embody a virtue you admire in this character. [name_m]Valor[/name_m], [name_u]Concord[/name_u], [name_f]Honor[/name_f], [name_m]Paladin[/name_m], [name_m]Prosper[/name_m], [name_m]Victor[/name_m], [name_u]August[/name_u], [name_u]Justice[/name_u], [name_m]Loyal[/name_m], [name_m]Clement[/name_m], [name_m]Hale[/name_m], and [name_u]Legend[/name_u] come to mind. Names like [name_m]Abel[/name_m] and [name_m]Abraham[/name_m] are more usable names of equally loyal sons; [name_m]Benjamin[/name_m] means “son of the right hand; son of my old age,” and [name_u]Dylan[/name_u] means “son of the sea,” which would be particularly appropriate given that Telemachus’s father was [name_m]Odysseus[/name_m]. “[name_m]Mac[/name_m]” just means “son of.”
And speaking of the sea, why not look at names related to water and adventure? [name_u]Sailor[/name_u], Venture, [name_m]Nemo[/name_m], [name_u]Murphy[/name_u], Antaeus, [name_u]Morgan[/name_u], [name_u]Kai[/name_u], Leomaris, [name_m]Marius[/name_m], [name_u]Merritt[/name_u], [name_m]Marvin[/name_m], [name_m]Zale[/name_m], Orman, [name_m]Perseus[/name_m], [name_m]Nereus[/name_m], Murrow, Mariner, Somerley, [name_m]Ferdinand[/name_m], [name_m]Fisher[/name_m], [name_u]Raleigh[/name_u], [name_m]Archer[/name_m], [name_m]Marco[/name_m], [name_m]Castor[/name_m], [name_m]Pollux[/name_m], [name_m]Nestor[/name_m], [name_m]Peregrine[/name_m], Faramond, [name_m]Romer[/name_m], [name_m]Arvad[/name_m], [name_m]Brendan[/name_m] (all found via ThinkBabyNames, if you want to look up meanings).
The sounds of Telemachus sort of evoke [name_m]Talmadge[/name_m] to me. [name_m]Talmadge[/name_m] is rare as a first name and as a surname, but has some history of use in the US. What else…you could go for the faintly similar rhythm of [name_m]Atticus[/name_m] or [name_m]Thaddeus[/name_m]. There are some good suggestions above. Going with Odyssey, I think [name_m]Ulysses[/name_m] is due for a revival.
What’s so unusable about it? It sounds like a nice, strong name and changing anything takes away its character. And names like this are the reason we have nicknames. I knew a boy named Tellaferro (I think that’s the spelling) but he went exclusively by [name_m]Telly[/name_m]. Telemachus could go by [name_m]Telly[/name_m], [name_m]Mack[/name_m], [name_u]Max[/name_u], [name_m]Lem[/name_m], etc. If it’s still too much as a fn, then stick it in the middle as is
Telemachus puts me in mind of [name_m]Lemuel[/name_m]…
Other than that, I like the idea of using the actual name, but putting it in the middle.
I would just look for another inspirational figure from history.
This… or I’d go with what @augusta_lee suggested (pg 1).
However, I do think that once you alter a name too much - almost beyond recognition of the original inspiration it might be better to just search for new inspiration.