amnesia

Amnesia comes from modified Latin amnesia, borrowed from Ancient Greek ἀμνησία (amnēsía, 'forgetfulness'). That Greek word is formed from μιμνήσκω (mimnḗskō, 'to remind, to remember') with the alpha privative attached, the little prefix that negates or removes.

The word has stayed close to its root meaning throughout — it names the state of not-remembering, passing from Greek into Latin and then into English largely intact in sense.

The facts here don't name a specific English cognate, but the root verb mimnḗskō ('to remember') is worth noting as the word's living core, with the alpha privative simply stripping that meaning away.