Shakespeare did not use the word pantaloons. He did use the word
"Pantaloon", the name of a character in the Commedia dell'Arte, an
old and lecherous man. Gremio in The Taming of the Shrew is
described as a Pantaloon. It is in this sense that he uses it in
Jaques' Ages of Man Speech in As You Like It, where he says that
the sixth age slips into the lean and slippered Pantaloon.