🤔 Why Do XRP, XLM, XDC begin with X? 🤔
X currencies (funds, precious metals, supranationals, other)
In addition to codes for most active national currencies ISO 4217 provides codes for "supranational" currencies, procedural purposes, and several things which are "similar to" currencies:
Codes for the precious metals gold (XAU), silver (XAG), palladium (XPD), and platinum (XPT) are formed by prefixing the element's chemical symbol with the letter "X". These "currency units" are defined as one troy ounce of the specified metal.
The code XTS is reserved for use in testing.
The code XXX is used to denote a "transaction" involving no currency.
There are also codes specifying certain monetary instruments used in international finance, e.g. XDR is the symbol for special drawing right issued by the International Monetary Fund.
The codes for most supranational currencies, such as the East Caribbean dollar, the CFP franc, the CFA franc BEAC and the CFA franc BCEAO. The predecessor to the euro, the European Currency Unit (ECU), had the code XEU.
The use of an initial letter "X" for these purposes is facilitated by the ISO 3166 rule that no official country code beginning with X will ever be assigned.
The inclusion of EU (denoting the European Union) in the ISO 3166-1 reserved codes list allows the euro to be coded as EUR rather than assigned a code beginning with X, even though it is a supranational currency.
Source: https://en.wikipedia.org/wiki/ISO_4217#X_currencies_(funds,_precious_metals,_supranationals,_other)