There is a reason why the words ‘holy’ and ‘health’ have common root in a word that means ‘whole’, and that is because the concepts have a significant overlap, while being developed in certain different ways.
To be holy is, basically, for an organism to be functioning well, and in particular as relates to God, i.e., the Good. This suggests states not just of what we would call ‘well being’ in a secular sense, but also things from a Christian perspective like an indwelling presence of the Holy Spirit, say, and more generally having a disposition of aligning oneself with and being guided by God.
To be healthy is, basically, for an organism to be functioning well, but it doesn’t specify something like God, so the concept as it is typically used in English-speaking culture has a secular or agnostic virtue to it.
In both cases, there is an idea of ‘wholeness’, or well-integrated functioning of an organism that brings it towards what is good.
In its essence, I think, it is useful to conceive of ‘holiness’ in its full state as including the secular concept of health, but then adding to it by drawing out and emphasizing a spiritual component of health in addition.
(Indeed, in Christianity ‘Heaven’ is a society that is brought about where citizens have vigorous, robust, bodily or physical health. Similarly, consider the idea in Christianity that the Christ is ’the way [to God], the truth, and the life.’)
It seems obvious on reflection that optimum human functioning includes something like a spiritual aspect, and therefore the concept of holiness is or can be useful, whether one is monotheistic, polytheistic, atheistic, or what have you.