From Middle English pilfre (“booty”), from Old French pelfre (“plunder, booty, spoils”), of unknown origin. Possibly related to pelf.
pilfer (third-person singular simple present pilfers, present participle pilfering, simple past and past participle pilfered)
- To steal in small quantities, or articles of small value; to practise petty theft.
Derived terms 
to steal in small quantities