Irrealis mood and non-finite verbs

I am wondering if there is (cross-linguistically) a connection
between irrealis mood and non-finite verbs (or adjectives or nouns).
I know David Peterson calls a certain marker in Sidaan "irrealis/non-
finite marker", which seems to justify the vague impression I have
that they are related somehow. Maybe David could help me out with the
nuances of that marker in Sidaan (and in natlangs that may have
inspired it)?

Also, is there some linguistic term for the sort of connection I'm
thinking of? -- to wit, a kind of affinity or tendency for forms of
different kinds to be related in some way (either diachronically or
synchronically), or especially for the *same* form to be used to mark
different things?

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