The name "Katlain" is spelled with the letter "k" instead of the more common "c" because it is derived from the Gaelic name "Caitlín," pronounced /ˈkatʲliːnʲ/. The sound /k/ is represented by "k" in English, while "c" typically represents a softer sound like /s/ or /t͡ʃ/. Therefore, the spelling of "Katlain" accurately reflects the pronunciation of its Gaelic origin. However, some may still spell the name as "Caitlin" in English to reflect the more common spelling convention.