Italian smarrire means 'to lose; mislay'. It's from Germanic (Frankish) marrjan 'to anger; embarrass'. Cf. Spanish, Catalan marrir 'to lose'. The prefix s- epresses contrary action, or in this case, it's a privative-pejorative prefix. It's from Latin ex 'out of'. The past participle of the verb occurs in the opening lines of Dante's Divine Comedy:

Nel mezzo del cammin di nostra vita
mi ritrovai per una selva oscura
ché la diritta via era smarrita.

In the middle of the road of our life
I found myself in a dark wood
the right way having been lost.

Ceci n'est pas un seing.