What exactly does "carriers of utility" mean? I understand what 'utility' mean in economics.

While reading "Choices, Values, and Frames" by Daniel Kahneman I encountered above usage. I guess it means 'what utility is attributed to'. Google showed that this usage is common in economics literature, but I couldn't find a definition or an explanation.

What is the definition, if there is one? And if not, how best to interpret this phrase?

(Edit) Examples:
From above book (p-xii):


The proposition that the carriers of utility are states of wealth is accepted as a matter of course in economic analyses and in the prescriptions of decision analysis.
The idea that the effective carriers of utility are gains and losses was not now.


In "Decision, Probability and Utility: Selected Readings" by Peter Gärdenfors and Nils-Eric Sahlin:


As regards the conceptualization of utility, a fundamental question is what kids of entities can be assigned utilities. Or in other words, what are the carriers of utility? ...
This expression is used for the arguments of the utility function, that is, for the objects the agent "cares about". In the canonical model, the only carrier of utility is wealth, but in behavioral economics a lot of things can be considered (beliefs, wealth compared to a reference point, ...).

For instance, saying that the carrier of utility for John is the difference between John's wealth and Lisa's wealth means that the utility function of John is of the form $u(x-y)$ where $x$ is John's wealth and $y$ is Lisa's wealth. It is another way of saying that the only thing that matters to John is his relative wealth compared to Lisa, and not his absolute wealth.