Ka'b
Yes. Ka'b is attested in early Islamic biographical and historical sources for multiple historical figures, including companions and poets.
Lexically, كَعْب (kaʿb) means 'heel' or 'ankle' in classical Arabic dictionaries.
No proper-name occurrence of Ka'b appears as a named person in the Quran; attestations are found in sira and hadith literature.
Yes. It is historically grounded and short; some families use it for its classical Arabic root, though it is rare in contemporary use.
Yes. Examples include the Companion Kaʿb ibn Mālik and the poet Kaʿb ibn al-Ashraf, both recorded in early Arabic sources.