This proper name qualified for our onomatopoeia tag.  It hints that we have all heard and been surrounded by ancient raven-tongue our whole lives and have simply not the wit to hear this lingering remnant of the Third Age.

Tolkien himself writes in his Essay on Phonetic Symbolism about the origin of this name – and of his father’s

rook is no longer krāg or krāk or χrk from which it took its use.

• 15.014 I am Roäc son of Carc.
• 15.017 said Roäc.
• 15.021 Roäc Carc’s son.
• 15.022 croaked Roäc,
• 16.005 said Roäc,
• 17.030 but Thorin sent messengers by Roäc

Tolkien, J. R. R.. A Secret Vice: Tolkien on Invented Languages (Kindle Locations 1954-1955). HarperCollins Publishers. Kindle Edition.