The Tinman in the Wizard of Oz set out with Dorothy (and the Scarecrow and the Lion) to the Wizard to get a heart, presumably so that he can have feelings, emotions and perhaps to be tender hearted. Unknowingly, in the story, he already shows his “heart” through his actions and thoughts. Eventually the Wizard of Oz did give him a fake heart made of silk and filled with sawdust.
Sometimes what we think we lack is what we already possess, although its appearance is not what we or other expect. Indeed appearances can be deceiving. This reminds me of the Alchemist by Paulo Coelho.
Another possible interpretation out of the myriad number of interpretation is: what the Wizard can “give” or bestow is what the Tinman already “possess”. This made me think of poor people who struck the lottery and became poor again although I appreciate that this is off-tangent and may not be common among lottery winners. Phrased another way – one who’s not ready for something or someone would not possess that something/someone for long even when one is gifted that.