The four knaves (called in French, valets or varlets) are four
valiant captains--Ogier and Lancelot, the companions of
Charlemagne, Hector de Gallard, and Lahire, the generals of
Charles VII. The remainder of the pack equally presents a sort
of martial allegory; the heart is bravery; the spade (espad,
'sword') and the diamond (carreau, that is, a square or shield)
are the arms of war; the club (in French trefle, 'trefoil') is
the emblem of provisions; and the ace (in French as, from the
Latin aes, 'coin') is the emblem of money--the sinews of war.
In accordance with this allegorical meaning, the function of the
ace is most significant. It leads captive every other card,
queen and king included--thus indicating the omnipotence of gold
'To the mighty god of this nether world--
To the spirit that roams with banner unfurl'd
O'er the Earth and the rolling Sea--
And hath conquer'd all to his thraldom
Where his eye hath glanced or his footstep sped--
Who hath power alike o'er the living and dead--
Mammon! I sing to thee!
 Steinmetz Ode to Mammon.