Some details about the lore of the AST's arcanum deck, FYI, it's not a Jester, but a Knave in the deck. This is from the Encyclopedia Eorzea:
"The Deck of Sixty is most commonly divided into two distinct groups, the major arcana and the minor arcana. The six major arcana--the Spire, the Ewer, the Bole, the Arrow, the Balance, and the Spear--are said to represent the heavens and thus most often utilized in astrological and divinatory pursuits. Conversely, the minor arcana are believed to represent that land and its people, and feature six suits, each containing six cards numbered 1 through 6 (the pip cards0, and three face cards, for a total of fifty-four. Each suit possesses a corresponding element, class, and faculty, as well as direct tie to one of the six major arcana--all characteristics that can be employed (at the teller's discretion) during the scrying of a fortune."
A list of the six suits in the following order of detail:
Suit | Alternate | Faculty | Class | Element | Major Arcana
Crowns | Wreaths | Dominion | Nobility | Lightning | The Spire
Cups | Hearts | Emotion | Clergy | Water || The Ewer
Rings | Pentacles | Possession | Merchants | Earth | The Bole
Knives | Swords | Cognition | Military | Wind | The Arrow
Staves | Batons | Volition | Smallfolk | Fire | The Balance
Irons | Chains | Contrition | Prisoners | Ice | The Spear
"Face cards consist of the 'knave,' the 'lord,' and the highest-ranking 'lady.' When used in conjunction with the pip cards, their numerical values are 7, 8, and 9 respectively."
There's more, but this is I think the stuff not well known about. I'd love to integrate more aspects of this, such as having a Lord of Staves, or a Lady of Cups, rather than just the Crowns, and also include the Knave, but it gets convoluted very quickly. This is shared more just because I think it's interesting, not information that's easy to come by, and that there's a lot of worthwhile lore to try and build out of here, not to try and "um, actually" the reference to the Jester.