"In conclusion, it might be of some interest if I again record how I came to adopt the nom de crayon 'Spy'. Mr. Thomas Gibson Bowles, who was the proprietor of Vanity Fair at the time I submitted my first cartoon, requested me to invent some characteristic signature consisting of three letters. I worked three initials into the form and semblance of a jester's bauble. But that did not please him. Thereupon he threw me a dictionary, and asked me to choose a three-lettered word which would constitute an appropriate signature. The book opened in the middle of the 'S' pages. Near the top of the first column was the word 'Spy', one of the meanings of which was given as 'to observe'. Whereupon I adopted the word as a pencil-name, and I have caricatured under it ever since."
'Spy' and His Sitters Leslie Ward The Strand Magazine January 1910