Hi MTL:
Here is the definition for the club sandwich from the Cambridge:
club sandwich noun
![Coffee [C]](/emoticons/emotion-44.gif)
a sandwich made from three pieces of bread with meat, egg, cheese, salad or other cold food between them
It's very common in English, and in any other languages, to have different senses of meanings that apparently do not have any relations or similarities with each other. However, as long as they are put under the same entry in a dictionary, it means that they have the same root somewhere throughout the history, or they were related at some point . Meanings are always changing, sometimes it changes so much that the relation, visible sometime back, is no longer clear.
If they come from a different origin, or without any relations whatsoever, they are put under a seperate entry.
Just I have to remind you of this that in the dictionaries like the Cambridge, where seperate entries are chosen according to the sense, the method and the categorization is different to make readers find the meaning they are looking for much easier. In most of the dictionaries the method is different. For example, there is 3 seperateentries for the word "club" in the Oxford. The first considers the "group" sense, the second "the heavy stick ...", and a third entry defines the "playing cards" sense.
I hope it helps, good luck,