Oui oui, ma petite chica-D... eeeeeees vraiment non veirdahness eeen la lange du Francais.
In 1820, the French mathematician, André-Marie Ampère developed a theory and had it published. In the publication he used "I" for "intensité de current" (translates as intensity of current). The symbol for the intensity of current (now just called current in English) has been "I" ever since.
The units for current are called amperes (or just amps for short). One ampere is equivalent to one coulomb of charge per second.
Electrical Science and Signal Theory Timeline
(anyone feel like researching coulomb?) (I don't.)