Interesting to hear that the -ot diminutive in French, like in Charlot, is rather dated, in these Je suis Charlie times. Just like Charlot other diminutives have also taken on fixed identities of their own: Pierrot - and the double diminutive Guillotin (from Guillaume), which with a feminine ending, became the guillotine.
I wonder if the first ever recorded (royal) Charlotte was Charlotte de Bourbon (1388 - 1422), Queen of Cyprus. If so, funny coïncidence that she was the daughter of a Catherine - de Vendôme.