Five for one is a reference in William Shakespeare's

William Shakespeare

William Shakespeare was an English poet and playwright, widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist. He is often called England's national poet and the "Bard of Avon"...

 The Tempest to a traveller's insurance

Insurance

In law and economics, insurance is a form of risk management primarily used to hedge against the risk of a contingent, uncertain loss. Insurance is defined as the equitable transfer of the risk of a loss, from one entity to another, in exchange for payment. An insurer is a company selling the...

 practice conducted in medieval England

Kingdom of England

The Kingdom of England was, from 927 to 1707, a sovereign state to the northwest of continental Europe. At its height, the Kingdom of England spanned the southern two-thirds of the island of Great Britain and several smaller outlying islands; what today comprises the legal jurisdiction of England...

.

Origin

Because merchant-adventurers sailing from the Kingdom of England would usually not return, they could deposit money with an underwriter upon leaving and, upon their return, receive five times the deposited amount.

Gonzalo mentions that five for one insurance in scene 3 of act 3 of Shakespeare's The Tempest when he attempts to downplay the unfamiliarity of spirits he and his companions recently witnessed by comparing them to exotic creatures reported by the travellers who use such insurance. Since such travellers rarely returned alive, Gonzalo's reference to five for one does little to dispel his companions' fears.

Excerpt from The Tempest, Act 3, Scene 3

GONZALO

Faith, sir, you need not fear. When we were boys,
Who would believe that there were mountaineers
Dew-lapp'd like bulls, whose throats had hanging at 'em
Wallets of flesh? or that there were such men
Whose heads stood in their breasts? which now we find
Each putter-out of five for one will bring us
Good warrant of.