Spanish Gil and Polish Gil are a freak of coincidence. Neither are related to the other.
Another example is the root dur- means somethign entriely different in various languages:
In Enlglish and Latin-dervied tongues inclduign Psanish: strength, endurance, durability
In German (with an umlaut): something dry, parched or withered
In Polish and other Slavonic lingos: foolish, stupid, imbecilic (durak, dureń, durnocie)