Napoleon: the card game behind the nap
Racing borrowed the word nap from a card game, and the borrowing makes more sense once you know how the game worked.
The game
Napoleon, almost always shortened to Nap, is a trick-taking game for three or more players, best with five. Everyone is dealt five cards. Players then bid the number of tricks they think they can win, the highest bidder chooses trumps, and play begins.
Its rules were published by H. E. Heather in The Bazaar in October 1875, and the game spread quickly. It pushed Loo aside to become the most popular five-card game in England, which is why a card term ended up in the vocabulary of a completely different pastime.
The bid called nap
A player could bid three or four. Bidding nap meant committing to win all five tricks — the highest ordinary call in the game, and the one with no margin in it. Take four tricks having bid nap and you have failed just as surely as if you had taken none.
The stakes matched the risk. A successful nap won ten units from every other player at the table; a failed one paid five to each. Against four opponents that is forty units won or twenty lost on a single hand.
Some versions added calls above nap for players who wanted still longer odds. Wellington and Bonaparte both required all five tricks under an extra handicap, such as leading a particular card first.
Going nap
Because players announced their bids aloud — "I go two", "I go nap" — the phrase escaped the card table. To go nap entered English meaning to risk everything on one attempt, and separately to score five of something. Football commentators still say a player went nap when they score five goals in a match.
How racing took it
The transfer was natural. A racing correspondent publishes a dozen selections across an afternoon, and one of them has to be the one they would stand behind if forced to choose. That tip carries the same shape as the bid: no hedging, nothing held back, reputation on the line.
The card game faded. The word did not, and a hundred and fifty years later British and Irish papers still print a daily nap.
For how those daily naps are scored against each other across a season, see naps tables.