The sign for bad blended within a sign immediately tells us part of the meaning.
For example ill uses the bad hand slide along the chest. This location and chest movement tells us it is about a feeling. So the combined hand shape plus location means i feel bad = ill.
In strawberry the bad hand means the fruit is the bad fruit with the sign evolving through child allergies, don't feed babies this fruit its the bad fruit.
When you see emergency, even if you do not know the meaning the double bad hand immediately tells you its really bad! Bad luck adds the bad hand into the luck sign.