The word "杰克" is formed through a process of phonetic borrowing from English, specifically to approximate the sound of the name "Jack". It is constructed by selecting two pre-existing Chinese characters, 杰 (jié) and 克 (kè), whose combined pronunciation mimics the foreign name, with the characters chosen primarily for their sound rather than their individual meanings, resulting in a fixed, unanalyzed unit used to represent that specific foreign entity.