Swiftness means moving with great speed, prompt action, quick thinking. To be smart or clever.

The Eight of Wands is about: communicating, selling, promoting, marketing, making news about the actions. Hearing news about the action.

Book of Thoth – Swiftness

In the Eight of Wands, fire is no longer conjoined with the ideas of combustion and destruction. It represents energy in its most exalted and tenuous sense; this suggests such forms thereof as the electric current; one might almost say pure light in the material sense of that word.

Crowley saw this card as representing high energy physics.

The rainbow is prominent.

Magical Image of the First Face of Sagittarius in Picatrix

In the first face of Sagittarius ascends the form of a man armed with a coat of mail, and holding a naked sword in his hand; the operation of this is for boldness, malice, and liberty:

The first or Ascendant decan of Sagittarius is ruled by Mercury from November 22nd-Dec 1st

Mercury ruling this decanate of Sagittarius gives the sense of swiftness and ease of movement, to which we can add boldness and liberty from Picatrix. How the malice fits in is not so easy to establish.