A galoot is a person who is not graceful and does not dress neatly — big movements, clothes a bit wrong, always slightly in the way of the furniture. It is informal American English, often said with a grin rather than real spite, a bit like calling someone a big lump. You would not put it in a formal letter. The word is old slang; many younger speakers barely use it. The attested story traces it to the Arabic name Jālūt — Goliath, the giant in the Bible — as said in Egyptian Arabic, so the joke sitting inside it is “awkward giant.” That is the dictionary’s account; treat it as such, not as a story to embroider.

愣頭愣腦、粗手粗腳的傢伙（美式口語，常帶開玩笑，不是正經罵人）