* It's a misspelling: Perhaps you're thinking of a similar-sounding word. Could you be thinking of a different language, or a name?
* It's a regional dialect word: Greek has regional dialects with unique vocabulary.
* It's a modern borrowing or proper noun: Many words are borrowed into Greek from other languages. "Kala" might be a name or a word from another language used in a Greek context.
To help me understand what you're looking for, please provide more context. Where did you encounter this word?