while susurrus *is the Latin root.

Well, technically, susurrus and susurration are both Latin words. Though, the noun susurrus 'whispering, muttering' got verbed susurro (susurrare, susurravi, susurratus) 'to whisper, mutter', and the final form (past participle) of the verb got nouned susurratio 'whispering'. The Latin words, along with the related surdus 'deaf' go back to a PIE root *swer- ''; related to German schwirren 'to buzz, whirr; swish'. In Latin the first su- looks like either reduplication or some other root got glommed on to it.

Ceci n'est pas un seing.