This isn't a common English expression, but people use the word "soul" in different ways, "Pocketful of soul" is the name of a song, it's common in Motown music to use the word soul like this. Dictionary.com defines the use of "soul" in this way like this; Soul adjective "of, characteristic of, or for black Americans or their culture"

It sounds like a line from a song. In this context, “soul” probably means “spirit” or “intensity of emotion.” Depending on context, having a “pocketful” might mean having a lot, or maybe a little, soul.

is that name of a song ?