1
general::
Also, salt down. Keep in reserve, store, save, as in He salted away most of his earnings in a bank account. This idiom alludes to using salt as a food preservative. [Mid-1800s]
American Heritage Idioms
2
general::
Phrase(s): salt something away
1. Lit. to store and preserve a foodstuff by salting it. • The farmer’s wife salted a lot of fish and hams away for the winter. • She salted away a lot of food. 2. Fig. to store something; to place something in reserve. • I need to salt some money away for my retirement. • I will salt away some money for emergencies.
McGrawhill's American Idioms And Phrasal Verbs