"Calbert" is spelled with a "c" and not a "k" because it is derived from the Old English word "cealf," meaning calf. The "c" in "cealf" was pronounced as a "ch" sound, which gradually evolved into the "c" sound we use today. Therefore, "Calbert" is spelled with a "c" to retain its historical roots. The correct pronunciation of "Calbert" is /ˈkælbərt/, with stress on the first syllable.