'suffuse': How can you pour something (from) below?

I already understand so ask NOT about definitions, below which I instead purpose to burrow.
I heed the Etymological Fallacy.

ODO: Late 16th century: from Latin suffus- 'poured into', from sub- 'below, from below' + fundere 'pour'.

Etymonline entry for 'suffusion', to which the entry for 'suffuse' simply links: late 14c., from Latin suffusionem (nominative suffusio) "a pouring over," noun of action from past participle stem of suffundere "pour upon, overspread, suffuse," from sub "under" (see sub-) + fundere "to pour" (see found (v.2)).

Solution 1:

You are misinterpreting the origin. The intended meaning of the prefix sub- in this case is not from below; it is below. For suffuse, it changes the subject of the verb from the thing that does the pouring to the thing into which the pouring takes place. Here, below is used as a literal description, but also as an analogy.

Literal:

When you pour something from a jug to a cup, the cup is physically below the jug.

Analogy:

One who receives work from another is metaphorically below the person providing the work. —the thing being poured is the work.

Something is suffused from something that diffuses.