The origins of Telchar's name are extremely uncertain. It appears to be Elvish in form, and it probably represents his public name among the Elves, rather than his private Dwarvish name.
Its meaning is almost completely obscure. It's tempting to spy a connection to the root telep-, 'silver' (especially as Telchar's master Gamil Zirak had the Dwarvish word for silver as part of his name) but this is speculative at best. There is a Sindarin word telch, but that seems coincidental (its meaning is 'stalk' or 'stem', with no apparent connection to Telchar). The Elvish roots tel- and kar- could - just - be rendered as 'head-cover maker' (as a possible reference to Telchar's Dragon-helm), but this requires a very liberal interpretation.
Ultimately, it has to be said that the meaning of Telchar's name remains almost entirely mysterious.