From Max Cryer’s CURIOUS English words and phrases – the truth behind the expressions we use:
(Out for a) duck
Cricket usually has a visual scoreboard and if a player leaves the field having made no runs, a great big zero stands next to his or her name on the scoreboard. A practice arose many years ago of referring to this zero – because of its shape- as a duck’s egg, and this was shortened to just a duck. So if he or she was out for a duck, it means there was no score.
There is a similar development with the tennis score called ‘love’, which also signifies zero. Tennis originated in France, and when the player scored zero and that appeared on the board, the French thought exactly the same as the English – that it looked like an egg. So the French said a person’s score was l’oeuf (an egg). English people began to say it too but got it slightly wrong: l’oeuf became pronounced as ‘love’ and for the last 250 years, that’s the word the English language has used for a zero score in tennis.