The Ace of Coins is the plainest card in the deck: one coin, usually large, often bearing a maker's device. In the Mamluk deck from which the European suits descend, the equivalent suit is likewise coins, and the continuity is direct.
The renaming is a modern complication. Waite's deck calls the suit Pentacles and puts a five-pointed star on each coin, which imports an occult symbol into a suit that had been commercial currency for five hundred years. Crowley calls it Disks. Marseille-derived practice calls it Deniers, coins. These are not merely different words: a coin is money and a pentacle is a talisman, and the substitution shifts the whole suit from the economic to the magical. Readers who learned the suit as Pentacles frequently find its cards oddly spiritualised, and the reason is a naming decision made in 1909.
The Golden Dawn assigned the suit the element Earth, and the Ace, as with all the Aces, the root of that element's power rather than a discrete meaning.
Read practically, this card is a beginning with substance: money arriving, a job offered, a resource made available, a piece of work that will pay. Its distinctive quality among the Aces is that it is tangible; what it promises can be counted. The critical readings run to a beginning valued only for what it yields, or an opportunity taken because it is solid rather than because it is wanted.
The suit as a whole is the one most often underrated by readers who came to the cards for spiritual reasons, and the correction is worth making. Money, work, health and property are what most people actually consult an oracle about, and a suit devoted to them is not the shallow end of the deck.