What are the sets of things in SN 1.44? What are the sets of one, two, three, five and twelve things mentioned in the sutta below?
What does it mean?
From SN 1.44 (translated by Bhikkhu Sujato):

“One is the root, two are the whirlpools, three are the stains, five
the spreads, twelve the ocean’s whirlpools: such is the abyss crossed
over by the hermit.”

From SN 1.44 (translated by Bhikkhu Bodhi):

“The seer has crossed over
the abyss
With its one root, two whirlpools,
Three stains, five extensions,
An ocean with twelve eddies.”
There's a really long footnote here, which starts with a paraphrase of the commentary ...

This is a riddle verse the clue to which lies in the identification of the metaphors used. According to the comm., the root is craving; the two whirlpools (ie. 'dviraava.t.tam': rendered above as 'turning-twice') are the eternalist and annihilationist views; the three stains are lust, hatred and delusion; the five arenas are the five types of sense-pleasure; the ocean is craving itself in its insatiable aspect; the twelve eddies are the internal and external spheres (of sense) and the abyss is craving in its 'bottomless' aspect. (Note that craving plays a triple role in this interpretation).

... and which then goes on to doubt the commentary by pointing out that some of these metaphors are used to refer to other things in other suttas.