In Robert Louis Stevenson's The Strange Case of Dr. Jekyll and Mr. Hyde, the name "Utterson" may have been specifically chosen to support the story's plot.
In this case, "utter" is defined by Dictionary.com as:
to give audible expression to; speak or pronounce
TheFreedictionary.com defines "utter" as:
To articulate (words)
(note—it also says: To send forth with the voice: uttered a cry; however, in the context of the story, uttering a cry—as in being startled—would not apply to Utterson: he is quiet, as you say).
Cambridge Dictionaries Online defines "utter" as:
to say something or to make a sound with your voice
While some sites use different definitions, in terms of this story, all three of these definitions point less to "crying out," and more to speaking out. In Utterson's case, this seems to be exactly what he does: he becomes the storyteller who shares the details of what he learns up until the conclusion of the story, adding to the story's suspense. He is a lawyer who is presented as an ethical professional, and an intelligent, trustworthy, and credible "witness" to the events he shares from this strange tale.
However, your point is still well-taken. This is something I love to see readers do: looking for hidden symbolic meanings in the story, that allow one to search beneath the surface of the story, to another level of meaning. Oftentimes names are chosen very carefully by authors to provide clues, or to support the overall theme.
So even if "utter" does not fit with "to cry out," Utterson's name may still be very important. This ties in to why Utterson would be chosen as the story's narrator. If "utter" means to speak, articulate, or, in other words, to express oneself, this is exactly what Utterson does. He becomes the credible voice of reason who collects the confusing and misleading bits of information that surround the bond between Jekyll and Hyde in an effort to solve the mystery in the tale.
We might find irony in the fact that a lawyer is often in possession of secrets by clients which he cannot share; however, in this case Utterson is a lawyer with little information who must gather as much as possible in order for it to make sense to the other characters, but especially to the reader. Instead of defending a client, he has become the investigator.
By the end of the story, Utterson is the one who Stevenson has chosen to "utter" or articulate the events of the story so we finally understand that Jekyll and Hyde are the same person, and that this has been accomplished by Jekyll's experiments. Stevenson may have specifically chosen the name Utterson to reflect that this character would tell the story and answer the readers' questions by the story's end.
Additional sources for definitions: